Infrared high-sensitivity imaging detection method and spaceborne infrared camera

Abstract

The application discloses an infrared high-sensitivity imaging detection method and a satellite-borne infrared camera, and relates to the technical field of infrared imaging detection. The high-sensitivity infrared camera system comprises a linear high-gain infrared detector assembly, a low-temperature optical assembly and an information acquisition and processing integrated module. The information acquisition and processing integrated module comprises a multi-channel signal conditioning and acquisition circuit, an infrared background intelligent suppression circuit and an information processing and transmission circuit. The application can effectively solve the problem that the existing platform cannot adapt to the increasing optical aperture for improving the signal-to-noise ratio under the demand of weak and small target imaging detection, and the problem that the volume and weight of the imaging system are continuously increased, thereby avoiding the problem of repeated design and re-test verification, realizing the system miniaturization under the same signal-to-noise ratio or the great improvement of the signal-to-noise ratio under the same optical aperture, and solving the mismatch problem between the resource demand and the resources provided by the satellite-borne platform for improving the performance of the instrument and further increasing the optical aperture in the field of infrared imaging detection.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of infrared imaging and detection technology, in particular to an infrared high-sensitivity imaging and detection method and a spaceborne infrared camera. BACKGROUND

[0002] At present, the core device of modern infrared imaging system is focal plane array. With the continuous improvement of human demand for remote sensing field, especially the pursuit of high temporal resolution, high spatial resolution, high sensitivity and high spectral resolution, the infrared focal plane device has further developed rapidly in performance, scale and imaging speed.

[0003] In recent years, with the development of remote sensing technology, the demand for weak and small target infrared imaging and detection has also been increasing. In order to improve the detection and identification ability of weak and small targets, that is, to improve the radiation resolution ability, the optical aperture of infrared camera is continuously increased. The maximum size of a single mirror applied in space remote sensing field has reached 4 meters. Limited by processing technology and space application environment, it is difficult to further increase the size of single mirror. At present, the general method adopted internationally is to use small mirror to splice larger aperture telescope to improve sensitivity. A typical design is JWST (James Webb Space Telescope) which has been launched into orbit. However, this method requires high processing, installation and adjustment technology, and also puts forward more requirements for post-processing.

[0004] The existing infrared detector has rapidly expanded in scale. In current domestic and foreign spaceborne infrared cameras, large-scale infrared linear array detectors or area array detectors have been gradually applied. The scale of linear array detector reaches more than 2000 units, and the scale of single area array detector exceeds 1Kx1K pixels. The highest frame rate has exceeded 50 frames. JWST (James Webb Space Telescope) abroad uses 18 pieces of 4Kx4K infrared detectors. This brings the demand for improving the information acquisition speed of the detector. However, the faster the frame rate, the shorter the integration time, and the more difficult it is to improve the signal-to-noise ratio with a certain quantum efficiency of the detector.

[0005] Through the above analysis, the problems and defects of the prior art are: the traditional methods for improving the sensitivity of spaceborne infrared camera include increasing the optical aperture, selecting detectors with high quantum efficiency, and increasing the observation integration time. These methods are restricted by various factors and limit the further improvement of system sensitivity.

[0006] For the method of increasing the optical aperture, due to the envelope limit of the launch vehicle fairing, the camera optical aperture cannot be increased indefinitely, the large aperture optical assembly is affected by its own gravity, uneven temperature field, multi-point support stress and other factors to produce surface deformation, leading to defocus, distortion deterioration, and then affecting the imaging quality, bringing great difficulty to the design of system optics and support structure. In addition, the increase of aperture will inevitably lead to a sharp increase in weight and volume, and the demand for platform resources also increases rapidly, while the carrying capacity of the launch vehicle for different orbits is limited. On the other hand, the manufacturing cost will also increase sharply with the increase of the optical aperture, reducing the economic benefit. In recent years, large aperture lenses have been made by using active optical technology and small lens splicing to improve performance, but due to the limitations of consistency, installation precision, platform configuration layout and other factors, the performance improvement space is limited.

[0007] For the method of screening traditional infrared detectors with high quantum efficiency, although the signal-to-noise ratio can be improved, the quantum efficiency of traditional infrared detectors basically maintains a constant, which is difficult to further improve. Through screening, only detector modules with slightly lower noise and slightly larger response rate can be found, and the improvement of signal-to-noise ratio is limited under a certain integration time, which cannot meet the demand of short integration time and high frame rate fast imaging.

[0008] For the method of increasing the observation integration time, although the signal strength can be improved, noise will also be accumulated, such as the dark noise of the detector, the noise generated by the electrons excited by the space particles hitting the detector, and the infrared background of the instrument itself. In addition, in the case of high-speed target motion, long integration time leads to low frame rate, which cannot realize effective accumulation of the target in the energy dimension. Moreover, in the case of optical-mechanical scanning imaging, the integration time is directly limited by the optical-mechanical scanning imaging cycle. After the system time and space resolution is determined, the integration time cannot be prolonged, which also restricts the space for improving the signal-to-noise ratio.

[0009] The difficulty of solving the above problems and defects is: in the field of weak and small target infrared imaging detection, from the formula of point source signal-to-noise ratio, the traditional method or means to improve the sensitivity of spaceborne infrared camera in the application environment (height) is limited, the quantum efficiency of traditional detector basically tends to a constant, and the signal-to-noise ratio can only be improved by screening the detector, but it is difficult to greatly improve the signal-to-noise ratio, and the efficiency of screening is limited. Lengthening the integration time can effectively improve the signal-to-noise ratio, but the application occasion is different, and it cannot effectively improve the signal-to-noise ratio in the case of short integration time and high frame rate imaging. The most commonly used method is to increase the optical aperture to enhance the signal to improve the signal-to-noise ratio. However, it is difficult to meet the needs of resources, installation precision, high-precision control of structure deformation under vacuum thermal environment and other requirements by increasing the aperture, and it is difficult to improve the signal-to-noise ratio by orders of magnitude. Therefore, for an infrared detection system in a certain application environment, it is very difficult to effectively improve the signal-to-noise ratio and achieve high sensitivity detection. The existing technology can only improve a small amount with a huge cost and has a short plateaus. SUMMARY

[0010] In order to overcome the above problems, the present application provides an infrared high-sensitivity imaging detection method and a satellite-borne infrared camera. Through the design and analysis of the high-sensitivity infrared camera, based on the linear high-gain infrared detector assembly, the optical assembly, the information acquisition and processing integrated autonomous module, the problem that the existing platform cannot adapt to the increasing volume and weight of the imaging system caused by the increasing optical aperture for improving the signal-to-noise ratio is effectively solved, the problem of repeated design and re-test verification is avoided, the system miniaturization under the same signal-to-noise ratio or the great improvement of the system signal-to-noise ratio under the same optical aperture is realized, and the mismatch problem between the resource demand and the resources provided by the satellite-borne platform caused by the increasing optical aperture for improving the instrument performance in the field of weak and small target infrared imaging detection is solved.

[0011] The technical scheme adopted by the present application is:

[0012] An infrared high-sensitivity imaging detection method, comprising the following steps:

[0013] Step one, according to the spatial resolution, time resolution and detection signal-to-noise ratio requirements of the space infrared camera for target observation, selecting the imaging spectral range and distributing the system design parameters; introducing the energy concentration degree , the detector gain factor M into the point source signal-to-noise ratio formula, assuming that the required signal-to-noise ratio is SNR SYS , and deriving the demand for the gain factor M of the target detection infrared camera for the avalanche effect infrared detector;

[0014]

[0015]

[0016] Introducing the gain factor M into the noise equivalent temperature difference formula to measure the performance of the ground observation infrared camera, and deriving the demand for the gain factor M of the infrared detector;

[0017]

[0018]

[0019] In the formula:

[0020] : signal process factor; : atmospheric transmittance, : optical efficiency, : target radiation intensity;

[0021] : system F number, : system instantaneous field of view solid angle, System optical aperture Target energy concentration Target energy concentration Non-avalanche multiplication mode detector band detection rate, System noise equivalent bandwidth Signal-to-noise ratio Noise equivalent temperature difference

[0022] System F number: If the camera spatial angular resolution is defined as , then:

[0023]

[0024] is the camera focal length, and A is the detector area

[0025] Further, the gain factor expressed in terms of signal-to-noise ratio SNR and noise equivalent bandwidth NETD is respectively:

[0026]

[0027]

[0028] Step two, according to the constraint condition of the gain factor of the infrared detector, the imaging detection in the multiplication mode is carried out, and the low-voltage realizability of the bias, the stability and uniformity of the detector response are comprehensively considered. The gain factor M in the linear mode is generally taken as 10-20 as the best range for the imaging application occasion. If M exceeds 20, the system parameters are adjusted.

[0029] Step three, according to the above parameters, according to the constraint condition of the gain factor of the avalanche effect infrared detector, a suitable avalanche effect infrared detector is selected, and a suitable detector bias condition is set. Since the bias is positively correlated with the gain factor of the detector, but will affect the dynamic range, therefore, the bias is adjusted to make the gain factor of the detector meet the system requirements, and the demand of the dynamic range is considered. The influence on the dynamic range is mainly related to the calculation of the system noise in step two, and the effective signal range is determined by the following formula:

[0030]

[0031]

[0032] Therefore, in addition to meeting the demand of the gain factor, the selection of the bias voltage should also meet:

[0033]

[0034] In the formula, is the bias voltage ​The preamplifier gain of the detector is generally above 60dB; The integration time, The integration capacitor;

[0035] Step four, according to the above parameters, the low-temperature optical module, signal acquisition and processing integrated module is modular design; wherein the low-temperature optical module to the temperature gradient control of the mirror / transmission mirror should meet the demand of dynamic range, so that the instrument background response V b Meet the requirements of dynamic range;

[0036]

[0037] The Planck formula is used to calculate the spectral radiance of the components inside the instrument in the field of view of the detector , unit: W / m 2 / sr / μm.

[0038]

[0039] h is the Planck constant, 6.626×10 -34 J·s, k is the Boltzmann constant, 1.3807×10 -23 J·K -1 , ε is the emissivity, and λ is the wavelength. By integrating the spectral radiance L(λ, T) in the spectrum [λ1, λ2], then multiplied by the field of view angle , the detector pixel area A d , the instrument background light power P0 incident on the detector image plane is converted, and the value of V b is

[0040]

[0041] The dynamic range DR and the background level V b Constrain the temperature of the optical machine T, as the input of the low-temperature optical module design of the infrared camera;

[0042] The bias and power supply, timing, configuration, and signal interface of the avalanche effect mercury cadmium telluride infrared detector constitute the input of the information acquisition and processing integrated module, wherein the detector power supply, detector tap number, and readout frequency are the main input parameters.

[0043] Among them, the method for adjusting the system parameters in step two is: according to the camera bearing platform resources and the target imaging index, iterative optimization is carried out according to the evaluation index set until the optimal solution that meets the task demand and working condition is found, and the optimization of the parameters is converted into the optimal solution solving problem under multivariable;

[0044] The indicators most affected by the selection of the evaluation set for the infrared imaging system are the signal-to-noise ratio SNR, the noise equivalent temperature difference NETD, and the dynamic range DR; the formulas of SNR and NETD are shown in step 1, and the dynamic range DR is the ratio of the effective signal amplitude range of the system to the system noise; since the detector is the source output, the signal amplitude output by the detector can be used as the numerator, and the system coupling noise when the electronic channel gain is 1 can be used as the denominator; in the case where the noise components are not related, it can be calculated as:

[0045]

[0046] wherein, is the saturation output voltage of the detector, and the typical value of the detector powered by +3.3V to +3.6V is 2.5V; is the direct-current background signal of the detector output, which is related to the working bias setting; is the background signal of the instrument, which is affected by the instrument temperature field and the information acquisition circuit; is the dark current shot noise; is the readout circuit noise of the detector; is the thermal noise of the equivalent load resistance of the detector; is the photo-generated current shot noise; is the information acquisition circuit noise, which is ideally smaller than the readout circuit noise of the detector and can generally be ignored;

[0047] Further, , , readout circuit noise including output stage op-amp noise, power supply noise, sampling and holding circuit noise, reset noise, etc., which are independent of the photo-generated current , the dark current , and the gain factor M; in the formula: is the Boltzmann constant, is the electronic charge (1.6×10 -19 coulombs); is the environmental temperature (K), is the equivalent load resistance; is the bandwidth; is the integration time, is the integration capacitance; is the dark current, is the photo-generated current, including the signal photocurrent and the instrument background photocurrent; F(M) is the avalanche effect excess noise factor, which is defined as the ratio of the input signal-to-noise ratio of the device (the signal-to-noise ratio of the device without avalanche effect) to the output signal-to-noise ratio; in addition to meeting step 1, the value of M also needs to meet the constraint of the dynamic range:

[0048]

[0049] Furthermore, based on the three main evaluation indicators mentioned above, they are prioritized according to task requirements. Then, the impact of changes in the parameters involved in these evaluation indicators on the overall system performance is analyzed to identify the parameters that need to be optimized. When the adjustment of the parameters exceeds the design / manufacturing / testing boundary, M is adjusted appropriately. This process is repeated to adjust the iterative parameters until the system indicators that meet manufacturability are met.

[0050] Furthermore, the adjustable parameters in the analysis formula are analyzed, and the signal process factor is examined. For staring infrared cameras, the value is 1; for optomechanical scanning infrared cameras, the value is 0.667. Atmospheric transmittance For a camera with a defined spectral band, the optical efficiency can be considered a fixed value once the optical system configuration and the number of lenses are determined. It is also a definite value, the target radiation intensity These are definite values. Therefore, the optimizable camera configuration parameters include the camera aperture D0 and the detector pixel area A. d Noise equivalent bandwidth / integration time t int (For scanning systems) For the gaze system The system has six parameters: optical system F-number, gain factor M, and excess noise factor F(M).

[0051] The present invention also provides a spaceborne infrared camera based on an infrared high-sensitivity imaging detection method, including an avalanche effect mercury cadmium telluride infrared detector module operating in linear multiplication mode, a low-temperature optical module, a calibration module, and an integrated signal acquisition and processing module.

[0052] The low-temperature optical module includes an optical component composed of a reflector or a transducer, an aperture component, a structural support, a heat transfer pipe, a radiating plate component, and a temperature measurement and control component. The structural support and the aperture component are connected to the radiating plate component through the heat transfer pipe. The radiating plate component radiates heat to the external space, thereby enabling the entire optical component to reach thermal equilibrium under a predetermined low-temperature condition. The temperature measurement and control component is used for temperature monitoring and heating compensation.

[0053] The calibration module includes an on-board blackbody and a drive motor. The on-board blackbody is integrated with the light-blocking plate. The drive motor is used to open and close the blackbody plate. When the plate is open, it is used for Earth observation and imaging. When the plate is closed, it is used to heat and control the temperature of the plate and to collect blackbody data.

[0054] The integrated information acquisition and processing module includes a low-noise power supply circuit, a tunable detector bias circuit, a timing generation and detector configuration circuit, a multi-channel signal conditioning and acquisition circuit, an intelligent infrared background suppression circuit, and an information processing and transmission circuit.

[0055] Among them, the low-noise power supply circuit adopts the design method of source collection and branch independence, and centrally provides power supply for all circuits, including the low-noise power supply of the detector; each branch is set according to the difference of the load condition, and sets high-power switching power supply, low-voltage difference linear voltage regulation power supply, and low-noise small power supply; the high-power switching power supply is provided to the load after being filtered twice.

[0056] Among them, the tunable detector bias circuit includes a precision voltage reference, a high-precision current-mode DA converter, and a plurality of low-noise operational amplifiers; the DA converter receives input digital signals for digital-to-analog conversion, and then outputs a bias voltage after I-V conversion by the low-noise operational amplifier, which is provided to the detector.

[0057] Among them, the timing generation and detector configuration circuit takes FPGA as the core device, and includes a large-scale FPGA and an interface logic device, which is used for timing driving and parameter configuration of the detector, including integration capacitance and integration time.

[0058] Among them, the multi-channel signal conditioning and acquisition circuit includes a plurality of low-noise preamplifiers, a plurality of low-noise differential amplifiers, and a high-precision high-speed AD converter.

[0059] Among them, the infrared background intelligent suppression circuit includes a large-scale FPGA, a precision voltage reference, a high-precision current-mode DA converter, a high-precision high-speed AD converter, a plurality of low-noise operational amplifiers, a first memory, and a second memory; the FPGA and the high-precision high-speed AD converter are shared with the multi-channel signal conditioning and acquisition circuit; the infrared camera periodically automatically acquires and calculates data of the on-board blackbody, and when the difference between the response means of the current and previous two times of calibration data at the same temperature exceeds 10% or the image non-uniformity exceeds 5%, the cold space background is updated and recalibrated; the cold space instrument background data is acquired by the high-precision high-speed AD converter and stored in the first memory, and the background data is sent to the DA converter for recovery during imaging observation, and is sent to the front end for background subtraction operation, and the residual background is sent to the second memory for secondary subtraction operation at the digital end.

[0060] Among them, the information processing and transmission circuit includes a large-scale FPGA, a third memory, a fourth memory, and a high-speed transceiver interface circuit, and the FPGA is shared with the multi-channel signal conditioning and acquisition circuit and the infrared background intelligent suppression circuit; the FPGA generates all the timing of the camera, acquires image data for non-uniformity correction, geometric correction, and data calculation, the third memory stores intermediate operation process data, the fourth memory stores programs, and the high-speed transceiver interface circuit is used for receiving instructions and parameters and transmitting image data.

[0061] In combination with all the technical solutions above, the application has the advantages and positive effects that: the application can conveniently realize the improvement of the signal-to-noise ratio under a small caliber, and finally realize high-sensitivity imaging and detection with a small volume and weight of the infrared camera; or realize the improvement of the observation sensitivity by an order of magnitude while keeping the optical caliber unchanged. The application can effectively solve the problem of the increasing optical caliber of the infrared camera under the requirement of high radiation resolution, greatly improve the effectiveness and efficiency under the constraint of limited resources, improve the utilization rate of the platform, solve the contradiction between the improvement of imaging and detection performance and the requirement of resources, and play a significant role in the imaging and detection related fields such as meteorological satellites, land observation satellites, ocean observation satellites, deep space exploration, and small asteroid defense. For the observation imaging infrared camera, the application has good expansion capability and can be applied to platforms such as satellites and aircrafts, and through the splicing of the fields of view of multiple platforms, high-sensitivity detection of a large field of view can be realized.

[0062] The technical solution of the application is applied to an optical-mechanical scanning type infrared camera based on a linear infrared detector, meets the data acquisition requirement, and good application effects are obtained. In the linear multiplication mode, the 50mm caliber infrared camera using a 512-element avalanche effect linear infrared detector reaches the radiation resolution of a 150mm caliber infrared camera, and the application effects of the application are obvious compared with the traditional design method of increasing the caliber. The application results show that the method meets the requirement of high-sensitivity imaging and detection, has good expansibility, is suitable for application in a high-frame-rate space infrared camera, and can also be applied to a space infrared camera using optical-mechanical reciprocating scanning, and is conducive to the further development of remote sensing technology. BRIEF DESCRIPTION OF DRAWINGS

[0063] Figure 1 is a flow chart of an infrared high-sensitivity imaging and detection method provided by an embodiment of the application.

[0064] Figure 2 is a structure diagram of a high-sensitivity spaceborne infrared camera provided by an embodiment of the application.

[0065] Figure 2 In the figure: 1, avalanche effect infrared detector module / assembly; 2, low-temperature optical module; 3, optical assembly; 4, diaphragm assembly; 5, structure support; 6, heat pipe; 7, radiation plate assembly; 8, temperature measurement and control assembly; 9, calibration module; 10, on-board black body / shutter; 11, driving motor; 12, signal acquisition and processing integrated module; 13, low-noise power supply circuit; 14, tunable detector bias circuit; 15, timing generation and detector configuration circuit; 16, multi-channel signal conditioning and acquisition circuit; 17, infrared background intelligent suppression circuit; 18, information processing and transmission circuit. DETAILED DESCRIPTION

[0066] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0067] In view of the problems in the prior art, the present application provides an infrared high-sensitivity imaging detection method and a high-sensitivity spaceborne infrared camera, which will be described in detail below with reference to the drawings.

[0068] The infrared high-sensitivity imaging detection method and the high-sensitivity spaceborne infrared camera provided by the present application can also be implemented by other steps by ordinary skilled persons, Figure 2 The high-sensitivity spaceborne infrared camera provided by the present application is only a specific embodiment.

[0069] Embodiment 1

[0070] According to application requirements, for a working orbit H=3000km, a ground observation ground resolution r=300m, and a ground object detection working waveband 3.20-4.20um camera configuration parameter optimization, the camera working performance is required to be greater than 1 frame / s, SNR≥100, DR≥1000, and NETD≤0.5K.

[0071] The present application provides an infrared high-sensitivity imaging detection method, and the design steps are as follows.

[0072] Step 1: According to the spatial resolution, time resolution, and detection signal-to-noise ratio of the spaceborne infrared camera for target observation, the imaging spectrum is 3.50-4.20um, and the system design parameters are allocated, and the required signal-to-noise ratio is SNR SYS ≥100, according to step one, it can be deduced that the requirement of the infrared camera for the gain factor M of the avalanche effect infrared detector is M≥14, and M=15 is taken.

[0073] The table is listed as follows:

[0074] Table 1 Preliminary system design parameters

[0075]

[0076] Step 2: In order to image and detect in the multiplication mode, the low-voltage bias realizability, the detector response stability and uniformity are comprehensively considered, and the gain factor M in the linear mode is generally taken as 10-20, which is the best range for imaging application occasions, if M exceeds 20, the system parameters are adjusted, and the adjustment method is: according to the camera bearing platform resources and the target imaging index, the evaluation index set is used for iterative optimization until the optimal solution that meets the task requirements and working conditions is found, and the parameter optimization is converted into a multivariable optimal solution solving problem.

[0077] Here M takes 15 to meet the requirement, and the dynamic range can reach 1100:1 according to the following formula, wherein the electronic noise needs to meet: ≤0.1mV, which is small compared with the noise of the detector readout circuit and the like, and can be ignored.

[0078]

[0079] After calculation and comparison, the camera aperture D0, the detector pixel area A d , the noise equivalent bandwidth / integration time t int , the optical system F number, the gain factor M, the excess noise factor F(M) and the like can keep the design values in step one and are not adjusted.

[0080] Step three, according to the above parameters, an avalanche effect infrared detector of 512x8 is selected according to the gain factor constraint condition of the avalanche effect infrared detector, and the detector bias condition V ref =1.15V is set.

[0081] Step four, the low-temperature optical module and the signal acquisition and processing integrated module are modularly designed. The temperature gradient control interval of the low-temperature optical module for the reflecting mirror / transmitting mirror is [200K, 210K], the input interface of the signal acquisition and processing integrated module is the 512x8 detector interface, the detector adopts +3.3V power supply, the tap number is 4, the readout frequency is 10MHz, and the signal conditioning circuit interface is designed accordingly.

[0082] Embodiment case 2

[0083] Another object of the present application is to provide a spaceborne infrared camera for implementing the infrared high-sensitivity passive imaging detection method, and the high-sensitivity imaging detection infrared camera comprises an avalanche effect mercury cadmium telluride infrared detector module working in a linear multiplication mode, a low-temperature optical module, a calibration module and a signal acquisition and processing integrated module. The application of the method in the implementation of the infrared camera is as follows:

[0084] 1) A push-broom type infrared camera with an optical aperture of 100mm and a focal length of 400mm, which adopts a 512x8 avalanche effect mercury cadmium telluride mid-wave infrared detector module with a gain factor of 10.

[0085] 2) The low-temperature optical module comprises an off-axis three-mirror lens and a turning plane mirror, an internal secondary mirror diaphragm, an invar structure support, a double-channel heat transfer heat pipe, an OSR radiation plate assembly (with an area of 1 square meter), a 32-channel temperature measurement and control, and a structure support and diaphragm assembly connected to the radiation plate assembly through the heat transfer heat pipe. The OSR radiation plate assembly radiates heat to the external space, so that the whole optical assembly reaches thermal equilibrium under the condition of 200K low temperature, and the temperature measurement and control assembly is used for temperature monitoring and heating compensation.

[0086] 3) The calibration module includes an on-board blackbody and a driving motor. The on-board blackbody is designed integrally with a light barrier. The driving motor is used for opening and closing the blackbody light barrier. When the light barrier is opened, the ground observation imaging is performed. When the light barrier is closed, the blackbody data acquisition is performed by heating and temperature control of the light barrier. The blackbody temperature control point can be adjusted by an instruction, and the default is 20℃.

[0087] 4) The information acquisition and processing integrated module includes a low-noise power supply circuit, a tunable detector bias circuit, a timing generation and detector configuration circuit, a multi-channel signal conditioning and acquisition circuit, an infrared background intelligent suppression circuit, an information processing and transmission circuit.

[0088] Further, the low-noise circuit adopts a design mode of source collection and branch independence. DVTR2805SF and DVHF2815DF are used to convert the +28V power supply provided by the platform, and to centrally provide power supply for all circuits of the camera, including low-noise power supply +3.3V for the detector. According to the differences in load conditions, each branch is provided with a high-power switching power supply (RSS0508H), a low-dropout linear voltage regulator (RHF4913), and a low-noise low-power power supply (LW5101-00). The high-power switching power supply is provided to the load after being filtered twice.

[0089] Further, the tunable detector bias circuit includes a precision voltage reference LTC6655, a high-precision current-mode DA converter AD5542, and a multi-channel low-noise operational amplifier LM6142. The DA converter receives input digital signals for digital-to-analog conversion, and then outputs a bias voltage after I-V conversion by the low-noise operational amplifier LM6142, which is provided to the detector.

[0090] Further, the timing generation and detector configuration circuit takes FPGA as a core device, including a large-scale FPGA and an interface logic device, which is used for timing driving and parameter configuration of the detector, including integration capacitance and integration time. The FPGA adopts XILINX 7 series FPGA XC7K325T-FF900I.

[0091] Further, the multi-channel signal conditioning and acquisition circuit includes a multi-channel low-noise preamplifier AD8042, a multi-channel low-noise differential amplifier AD8138, and a high-precision high-speed AD converter AD6445.

[0092] Further, the infrared background intelligent suppression circuit includes a large-scale FPGA XC7K325T-FF900I, a precision voltage reference standard LTC6655, a high-precision current-mode DA converter AD5542, a high-precision high-speed AD converter AD6445, a multi-channel low-noise operational amplifier LM6142, a first storage (3DPLUS company's SDRAM 3DSD1G32VS2490), and a second storage (3DPLUS company's SDRAM 3DSD1G32VS2490). The FPGA, the high-precision high-speed AD converter, the multi-channel signal conditioning and acquisition circuit share the same. The infrared camera regularly performs data acquisition and calculation on the on-board black body. When the response mean difference of the current and previous two times of calibration data at the same temperature exceeds 10% or the image non-uniformity exceeds 5%, the cold space background update is started, and recalibration is performed. The cold space instrument background data is obtained by the high-precision high-speed AD converter and stored in the first storage. During imaging observation, the background data is sent to the DA converter for recovery and sent to the front end for background subtraction. The residual background is sent to the second storage (3DPLUS company's SDRAM 3DSD1G32VS2490) for secondary subtraction operation at the digital end.

[0093] Further, the information processing and transmission circuit includes a large-scale FPGA (XC7K325T-FF900I), a third storage (3DPLUS company's SDRAM 3DSD1G32VS2490), a fourth storage (3DPLUS's FLASH 3DFO256M16VS4269), and a high-speed transceiver interface circuit (TI company's TLK2711). The FPGA shares the same with the multi-channel signal conditioning and acquisition circuit and the infrared background intelligent suppression circuit. The FPGA generates all the camera timing and obtains image data for non-uniformity correction, geometric correction, data calculation, etc. The third storage stores the intermediate operation process data, the fourth storage stores the program, and the high-speed transceiver interface circuit is used for receiving instructions and parameters and transmitting image data.

[0094] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any modification, equivalent replacement and improvement within the technical range disclosed by the present application, which is within the spirit and principles of the present application, should be covered within the protection scope of the present application.

Claims

1. A high-sensitivity infrared imaging detection method, characterized in that: Includes the following steps: Step 1: Based on the spatial resolution, temporal resolution, and signal-to-noise ratio requirements of the space infrared camera for target observation, select the imaging spectral band and allocate system design parameters; introduce energy concentration into the point source signal-to-noise ratio formula.

1. Detector gain factor M, assuming the required signal-to-noise ratio is SNR. SYS The requirements of the gain factor M of the infrared detector for the avalanche effect of the infrared camera for target detection are derived; the gain factor M is introduced into the noise equivalent temperature difference formula to measure the performance of the infrared camera for earth observation and to derive the requirements of the gain factor M of the infrared detector. Step 2: Based on the constraints of the infrared detector gain factor, imaging detection is performed in multiplication mode. The system parameters are adjusted by comprehensively considering the feasibility of low-voltage bias, detector response stability and uniformity. Step 3: Based on the above parameters and the gain factor constraint of the avalanche effect infrared detector, select a suitable avalanche effect infrared detector and set appropriate detector bias conditions. Since the bias is positively correlated with the detector gain factor, but it will affect the dynamic range, the bias is adjusted so that the detector gain factor meets the system requirements and takes into account the dynamic range requirements. Step four: Based on the above parameters, modularly design the low-temperature optics module and the integrated signal acquisition and processing module; among them, the temperature gradient control of the low-temperature optics module for the reflector / transmitter should meet the dynamic range requirements, so that the instrument background response V b Meeting the dynamic range requirements; determined by the dynamic range (DR) and background level (V). b The constrained optomechanical temperature T serves as the input for the design of the low-temperature optical module of the infrared camera; the bias and power supply, timing, configuration, and signal interface of the avalanche effect mercury cadmium telluride infrared detector constitute the input for the integrated information acquisition and processing module, among which the detector power supply, the number of detector taps, and the readout frequency are the main input parameters.

2. The infrared high-sensitivity imaging detection method according to claim 1, characterized in that: The method for adjusting system parameters in step two is as follows: based on the camera platform resources and the target imaging indicators, iterative optimization is performed according to the evaluation index set until the optimal solution that meets the task requirements and working conditions is found, thus transforming the parameter optimization into a problem of finding the optimal solution under multiple variables.

3. A spaceborne infrared camera for implementing the infrared high-sensitivity imaging detection method according to claim 1, characterized in that: It includes an avalanche effect mercury cadmium telluride infrared detector module operating in linear multiplication mode, a low-temperature optical module, a calibration module, and an integrated signal acquisition and processing module; The low-temperature optical module includes an optical component composed of a reflector or a transducer, an aperture component, a structural support, a heat transfer pipe, a radiant plate component, and a temperature measurement and control component. The structural support and the aperture component are connected to the radiant plate component through the heat transfer pipe. The calibration module includes an on-board blackbody and a drive motor, with the on-board blackbody and the light-blocking plate integrated into a single design. The integrated information acquisition and processing module includes a low-noise power supply circuit, a tunable detector bias circuit, a timing generation and detector configuration circuit, a multi-channel signal conditioning and acquisition circuit, an intelligent infrared background suppression circuit, and an information processing and transmission circuit.

4. A spaceborne infrared camera according to claim 3, characterized in that: The low-noise power supply circuit adopts a source-centralized, branch-independent design, centrally providing power to all circuits, including the low-noise power supply for the detector; each branch is configured with a high-power switching power supply, a low-dropout linear regulated power supply, or a low-noise low-power power supply according to the difference in load conditions; the high-power switching power supply is provided to the load after secondary filtering.

5. A spaceborne infrared camera according to claim 3, characterized in that: The tunable detector bias circuit includes a precision voltage reference, a high-precision current-mode DA converter, and multiple low-noise operational amplifiers. The DA converter receives the input digital signal, performs digital-to-analog conversion, and then performs IV conversion through the low-noise operational amplifiers to output a bias voltage, which is then provided to the detector.

6. A spaceborne infrared camera according to claim 3, characterized in that: The timing generation and detector configuration circuit uses an FPGA as its core device, including a large-scale FPGA and interface logic devices, for timing drive and parameter configuration of the detector, including integrating capacitors and integrating time.

7. A spaceborne infrared camera according to claim 3, characterized in that: The multi-channel signal conditioning and acquisition circuit includes multiple low-noise preamplifiers, multiple low-noise differential operational amplifiers, and a high-precision, high-speed AD converter.

8. A spaceborne infrared camera according to claim 3, characterized in that: The intelligent infrared background suppression circuit includes a large-scale FPGA, a precision voltage reference, a high-precision current-type DA converter, a high-precision high-speed AD converter, multiple low-noise operational amplifiers, a first memory, and a second memory; the FPGA and the high-precision high-speed AD converter are shared with the multi-channel signal conditioning and acquisition circuit; the infrared camera periodically and automatically acquires and calculates data on the on-board blackbody. When the difference in the mean response of two consecutive calibration data at the same temperature exceeds 10% or the image non-uniformity exceeds 5%, the cold space background update is initiated and recalibrated. Background data of the cold space instrument is acquired by a high-precision, high-speed AD converter and stored in the first memory. During imaging observation, the background data is sent to the DA converter to recover the data and sent to the front end for background subtraction. The residual background is sent to the second memory and a second subtraction operation is performed at the digital end.

9. A spaceborne infrared camera according to claim 3, characterized in that: The information processing and transmission circuit includes a large-scale FPGA, a third memory, a fourth memory, and a high-speed transceiver interface circuit. The FPGA is shared with the multi-channel signal conditioning and acquisition circuit and the infrared background intelligent suppression circuit. The FPGA generates all the timing sequences of the camera and acquires image data for non-uniformity correction, geometric correction, and data calculation. The third memory stores intermediate calculation process data, the fourth memory stores the program, and the high-speed transceiver interface circuit is used to receive instructions and parameters and transmit image data.

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