Quantum efficiency testing method and system for infrared focal plane detector

Abstract

The application provides a quantum efficiency testing method and system for an infrared focal plane detector, comprising an infrared focal plane detector and a surface source black body arranged in alignment with the infrared focal plane detector and at a preset distance, so that the black body radiation uniformly irradiates on the pixel of the infrared focal plane detector, and the surface source black body works at a preset temperature; and comprising the following steps: step S1, acquiring the pixel voltage data of the pixel of the infrared focal plane detector under different integration times; step S2, linearly fitting the pixel voltage data of the infrared focal plane detector with the integration time, and determining the slope of the fitting straight line; step S3, acquiring the optical F number of the infrared focal plane detector, the integration capacitance of the readout circuit on the infrared focal plane detector, the pixel area and the Planck photon emission rate, and combining the determined slope of the fitting straight line to calculate the quantum efficiency. Advantageous effects: the testing method is simple and feasible, and the data acquisition is convenient and the data processing is simple.

Description

Technical Field

[0001] This invention relates to the field of infrared focal plane array detection technology, and in particular to a method and system for testing the quantum efficiency of an infrared focal plane array detector. Background Technology

[0002] Infrared focal plane detectors belong to the third generation of infrared imaging devices and are the core components of infrared systems. They have advantages such as high integration, low noise equivalent temperature difference, and strong detection capabilities, and are widely used in various fields such as military, industry, agriculture, medical, and forest fire prevention.

[0003] Quantum efficiency is a precise measurement of a device's photosensitivity. Since the energy of a photon is proportional to the reciprocal of its wavelength, quantum efficiency is typically measured over a range of wavelengths. The quantum efficiency of photographic films is usually less than 10%, while photocouplers can achieve efficiencies exceeding 90% at certain wavelengths.

[0004] There is currently no complete theory that can quantitatively analyze the calculation process of the quantum efficiency of infrared focal plane detectors and its influencing factors. Summary of the Invention

[0005] To address the above technical problems, this invention provides a method and system for testing the quantum efficiency of an infrared focal plane detector.

[0006] The technical problem solved by this invention can be achieved by the following technical solutions:

[0007] A method for testing the quantum efficiency of an infrared focal plane detector includes an infrared focal plane detector and a black body that is aligned with the infrared focal plane detector and separated from it by a preset distance, such that the black body radiation uniformly illuminates the pixels of the infrared focal plane detector, and the black body operates at a preset temperature.

[0008] And includes the following steps:

[0009] Step S1: Obtain pixel voltage data of the infrared focal plane detector at different integration times;

[0010] Step S2: Perform linear fitting on the pixel voltage data of the infrared focal plane detector with the integration time to determine the slope of the fitted line;

[0011] Step S3: Obtain the optical F-number of the infrared focal plane detector, the integrating capacitance of the readout circuit on the infrared focal plane detector, the pixel area, and the Planck photon emissivity, and calculate the quantum efficiency by combining the slope of the determined fitted line.

[0012] Preferably, acquiring the pixel voltage data of the infrared focal plane detector at different integration times specifically includes:

[0013] Obtain the output voltage of all pixels on the infrared focal plane detector;

[0014] The output voltages of all pixels are averaged to obtain the pixel voltage data at different integration times.

[0015] Preferably, after step S3, the method further includes:

[0016] Adjust the preset temperature, and measure and obtain the relationship between the pixel output voltage and the integration time after the preset temperature adjustment according to the process of steps S1-S3, so as to obtain the quantum efficiency at different blackbody temperatures.

[0017] Preferably, the quantum efficiency is calculated using the following formula:

[0018]

[0019] Wherein, F represents the optical F-number of the infrared focal plane detector; n represents the compensation coefficient; k represents the slope of the fitted line; C represents the integrating capacitance of the readout circuit; j represents the Planck photon emissivity; Ad represents the pixel area; and η represents the quantum efficiency.

[0020] Preferably, the Planck photon emissivity is determined using the following formula:

[0021]

[0022] Where λ represents the wavelength of the incident light radiated by the blackbody; h represents Planck's constant; c represents the speed of light in vacuum; T represents the preset temperature; K B denoted by Boltzmann constant; j represents the Planck photon emissivity.

[0023] Preferably, the preset temperature is 20℃-70℃.

[0024] Preferably, the infrared focal plane detector is a cooled infrared focal plane detector.

[0025] The present invention also provides a quantum efficiency testing system for an infrared focal plane detector, characterized in that the method for implementing the quantum efficiency testing method for the infrared focal plane detector as described above includes an infrared focal plane detector and a black body of the surface source arranged aligned with the infrared focal plane detector and separated by a preset distance, such that the black body radiation uniformly irradiates the infrared focal plane detector, and the black body of the surface source operates at a preset temperature.

[0026] Also includes:

[0027] The acquisition unit is used to acquire pixel voltage data of the infrared focal plane detector at different integration times;

[0028] A fitting processing unit, connected to the acquisition unit, is used to linearly fit the pixel voltage data of the infrared focal plane detector with the integration time and determine the slope of the fitted line.

[0029] The calculation unit, connected to the fitting processing unit, is used to obtain the optical F-number of the infrared focal plane detector, the integrating capacitance of the readout circuit on the infrared focal plane detector, the pixel area, and the Planck photon emissivity, and calculate the quantum efficiency by combining the slope of the determined fitting line.

[0030] Preferably, the acquisition unit specifically includes:

[0031] The acquisition module is used to acquire the output voltage of all pixels on the infrared focal plane detector;

[0032] The processing module, connected to the acquisition module, is used to average the output voltage of all pixels to obtain the pixel voltage data at different integration times.

[0033] Preferably, it further includes:

[0034] An adjustment unit is used to adjust the preset temperature to measure and obtain the relationship between the pixel output voltage and the integration time after the preset temperature adjustment, so as to obtain the quantum efficiency at different blackbody temperatures.

[0035] The advantages or beneficial effects of the technical solution of this invention are as follows:

[0036] The quantum efficiency testing method of the present invention is simple and feasible, with convenient data acquisition and simple data processing, and is suitable for focal plane detector devices with relatively small dark current. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating the quantum efficiency testing method for an infrared focal plane detector in a preferred embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram illustrating the change of pixel voltage with integration time in a preferred embodiment of the present invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0042] See Figure 1-2 In a preferred embodiment of the present invention, based on the above-mentioned problems existing in the prior art, a quantum efficiency testing method for an infrared focal plane detector is provided, including an infrared focal plane detector and a black body of the surface source arranged aligned with the infrared focal plane detector and separated by a preset distance, such that the black body radiation is uniformly irradiated on the infrared focal plane detector, and the black body of the surface source operates at a preset temperature.

[0043] And includes the following steps:

[0044] Step S1: Obtain pixel voltage data of the infrared focal plane detector at different integration times;

[0045] Step S2: Perform linear fitting on the pixel voltage data of the infrared focal plane detector with the integration time to determine the slope of the fitted line.

[0046] Step S3: Obtain the optical F-number of the infrared focal plane detector, the integrating capacitance of the readout circuit on the infrared focal plane detector, the pixel area, and the Planck photon emissivity, and calculate the quantum efficiency by combining the slope of the determined fitted line.

[0047] In a preferred embodiment, acquiring pixel voltage data of the infrared focal plane detector at different integration times specifically includes:

[0048] Obtain the output voltage of all pixels on the infrared focal plane detector;

[0049] The output voltage of all pixels is averaged to obtain pixel voltage data at different integration times.

[0050] In a preferred embodiment, after step S3, the method further includes:

[0051] Adjust the preset temperature, and measure and obtain the relationship between the pixel output voltage and the integration time after the preset temperature adjustment according to the process of steps S1-S3, so as to obtain the quantum efficiency at different blackbody temperatures.

[0052] In a preferred embodiment, the quantum efficiency is calculated using the following formula:

[0053]

[0054] Where F represents the optical F-number of the infrared focal plane detector; n represents the compensation coefficient; k represents the slope of the fitted line; C represents the integrating capacitance of the readout circuit; j represents the Planck photon emissivity; Ad represents the pixel area; and η represents the quantum efficiency.

[0055] In a preferred embodiment, the Planck photon emissivity is determined using the following formula:

[0056]

[0057] Where λ represents the wavelength of the incident light radiated by the blackbody; h represents Planck's constant; c represents the speed of light in vacuum; T represents the preset temperature of the blackbody; K B denoted by Boltzmann constant; j represents Planck photon emissivity.

[0058] In a preferred embodiment, the preset temperature is 20℃-70℃.

[0059] In a preferred embodiment, the infrared focal plane detector is a cooled infrared focal plane detector.

[0060] The present invention also provides a quantum efficiency testing system for an infrared focal plane detector, characterized in that the method for implementing the quantum efficiency testing method for the infrared focal plane detector as described above includes an infrared focal plane detector and a black body that is aligned with the infrared focal plane detector and separated from it by a preset distance, such that the black body radiation is uniformly irradiated onto the infrared focal plane detector, and the black body operates at a preset temperature.

[0061] Also includes:

[0062] The acquisition unit is used to acquire pixel voltage data of the infrared focal plane detector at different integration times;

[0063] The fitting processing unit, connected to the acquisition unit, is used to linearly fit the pixel voltage data of the infrared focal plane detector with the integration time and determine the slope of the fitted line.

[0064] The calculation unit, connected to the fitting processing unit, is used to obtain the optical F-number of the infrared focal plane detector, the integrating capacitance of the readout circuit on the infrared focal plane detector, the pixel area, and the Planck photon emissivity, and to calculate the quantum efficiency by combining the slope of the determined fitting line.

[0065] In a preferred embodiment, the acquisition unit specifically includes:

[0066] The acquisition module is used to acquire the output voltage of all pixels on the infrared focal plane detector;

[0067] The processing module, connected to the acquisition module, is used to average the output voltage of all pixels to obtain pixel voltage data at different integration times.

[0068] In a preferred embodiment, it further includes:

[0069] The adjustment unit is used to adjust the preset temperature to measure and obtain the relationship between the pixel output voltage and the integration time after the preset temperature adjustment, so as to obtain the quantum efficiency at different blackbody temperatures.

[0070] The embodiments of the present invention are further described below:

[0071] An infrared focal plane array (IRFPA) is a detector sensitive to infrared radiation and equipped with readout circuitry. The output voltage V of an IRFPA pixel (the sensitive element of the infrared detector) is... out (Also called signal voltage, unit: volt, V) is:

[0072]

[0073] Among them, V B This represents the output voltage of the readout circuit when the infrared focal plane is not yet activated. For charging-type readout circuits, ΔQ is positive; for discharging-type readout circuits, ΔQ is negative. ΔQ is an integral time t under fixed test conditions. int The amount of charge accumulated in the internal integrating capacitor C (unit: coulomb, C).

[0074] According to radiometry, at integration time t int The number of electron-hole pairs e generated by internally incident photons num for

[0075]

[0076] Where θ represents the field of view (FOV) of the infrared focal plane detector; α (i) represents the transmittance of the i-th optical element that the incident light passes through before reaching the pixel of the focal plane detector; A dη represents the pixel area of ​​a single pixel at the center of the infrared focal plane detector; η represents the quantum efficiency (i.e., the number of electron-hole pairs generated by each incident photon); j represents the Planck photon emissivity of light (in μm) at a temperature of T of the thermal radiation source (or blackbody) directly opposite the infrared focal plane detector device, with the radiation band ranging from λ1 to λ2.

[0077] According to radiometry, the Planck photon emissivity j is given by the following equation:

[0078]

[0079]

[0080] Where λ represents the wavelength of the incident photon (in μm); h represents Planck's constant, h = 6.626 × 10⁻⁶. -34 J·s; c represents the speed of light in a vacuum, c = 3.0 × 10⁻⁶ 14 μm / s; K B K represents the Boltzmann constant. B =1.38065×10 -23 J / K;

[0081] From the above formula (3), it can be seen that when the temperature T of the thermal radiation source (i.e., the surface source blackbody) is stable and the distance r from the infrared focal plane detector to the thermal radiation source remains constant, the radiation photon flux density received by the infrared focal plane in the band range of λ1~λ2 (unit μm) is:

[0082]

[0083] Furthermore, the radiation photon flux density is constant, meaning the number of photons received by a specific pixel on the infrared focal plane per unit time is constant. This also means the number of electron-hole pairs generated per square micrometer pixel per unit time is constant. Therefore, the quantum efficiency of the infrared focal plane is a stable value. Consequently, when temperature T and distance R remain constant, the signal voltage output value V of the infrared focal plane detector pixel remains constant. out With integration time t int It is a linear relationship, satisfying the following equation:

[0084]

[0085] V out -t int The slope k of the image satisfies the following relationship:

[0086]

[0087] Then the quantum efficiency η is

[0088]

[0089] Among them, the F-number of the infrared focal plane detector, the integrating capacitor C of the readout circuit (ROIC), and the pixel area A d All of these are known, and j can be obtained by integrating the response band of the infrared focal plane using equation (3). Therefore, to test the quantum efficiency η of the infrared focal plane, only the signal voltage output value V of the center pixel of the infrared focal plane needs to be collected for data acquisition. out Integration time t int The change relationship data, that is, the signal voltage data obtained by changing the integration time under normal operation of the infrared focal plane detector, is the signal voltage V. out Integration time t int The data is fitted to a straight line using the least squares method to obtain V. out -t int The slope k of the image, when substituted into equation (6), yields the quantum efficiency η of the focal plane of the MCT cooled infrared focal plane detector. Combined with the GB / T 17444-2013 Infrared Focal Plane Parameter Test Method, the approximate photon flux density incident on the pixel can be obtained from the following equation:

[0090]

[0091] When F>1, n takes the value 1; when F≤1, n takes the value 0. Substituting the above equation into equation (6), we have:

[0092]

[0093] The method of this invention for testing quantum efficiency can be summarized as testing the signal voltage at a fixed blackbody temperature and different integration times. That is, under the irradiation condition of blackbody temperature T, the signal voltage of the infrared focal plane detector at different integration times is collected. After the signal voltage is measured, the quantum efficiency of the infrared focal plane detector can be calculated according to the formula derived above.

[0094] In this embodiment of the invention, during the testing process, the infrared focal plane detector is aligned with the black body of the surface source through the optical system. The control module provides bias voltage and working pulse to the infrared focal plane to ensure its normal operation. The collected signals are processed and sent to the control module after signal processing and data acquisition. The control module interacts with the computer.

[0095] (1) Test conditions:

[0096] 1.1 The blackbody temperature is stable, and the original image is output without modulation;

[0097] 1.2 Blackbody radiation should ensure uniform irradiation of all pixels on the focal plane;

[0098] 1.3 When testing a surface source blackbody, the recommended blackbody temperatures are 20℃, 30℃, 40℃, 50℃, 60℃, and 70℃.

[0099] (2) The test steps are as follows:

[0100] 2.1 Test preparation: Connect to the test system and prefabricate the test system;

[0101] 2.2 Adjust the test system to apply the optimal bias voltage to the cooled infrared focal plane detector so that the detector is in normal working condition;

[0102] 2.3 At blackbody temperatures of 20℃, 30℃, 40℃, 50℃, 60℃, and 70℃, the integration time is changed via a serial port tool, and one frame of data is collected for each integration time. This yields a set of two-dimensional arrays for different integration times at each temperature.

[0103] 2.4 After measuring the two-dimensional array at the same temperature but different integration times, the quantum efficiency η can be calculated according to the formula derived above.

[0104] (3) Data acquisition and processing:

[0105] 3.1 A set of data on the time-varying integral time of the blackbody at temperatures of 20℃, 30℃, 40℃, 50℃, 60℃, and 70℃ was collected at room temperature.

[0106] 3.2 Locate the 16 pixels (or 9 pixels) at the center of the focal plane, and average their output voltages to obtain the pixel signal voltage data V at different integration times under the same temperature. out (T,t int ()).

[0107] 3.3 For the same temperature T, the pixel signal voltage V of the infrared focal plane detector out (T,t int ()) varies with integration time t int The processing of changing data depends on the characteristics of the readout circuit. For example, if the detector uses a direct injection (DI) readout circuit, its performance is poor at low luminous flux but is standard at high luminous flux. Capacitor transimpedance amplifier (CTIA) circuits are more complex and have higher power, but offer excellent linearity. Other types of readout circuits also have their characteristics and advantages / disadvantages described in relevant literature. Data processing should be based on the characteristics of these readout circuits. Therefore, for DI circuits, it is recommended to subtract data less than 10% and greater than 95% of the well depth. For CTIA circuits, due to their excellent linearity, no additional data subtraction is necessary.

[0108] 3.4 The previously processed infrared focal plane detector signal voltage V at the same temperature T out (T,t int ()) varies with integration time t int The changing data was fitted with a straight line using Origin software to obtain V. out -t int The slope k of the fitted line in the image can be used to calculate the quantum slope η of the detector using formula (7), where C is given by the integrating capacitor of the readout circuit, and A d Given the pixel specifications of the focal plane detector, j is obtained by integrating the spectral response band range λ1~λ2 (unit μm) of the infrared focal plane detector using integral formula (3). Taking a cooled mid-wave infrared focal plane detector as an example, a F4 infrared focal plane detector of model MM615S4S3 was tested. Its spectral response range is 3.7~4.8 (unit μm). The value of j in the mid-wave band of 3.7~4.8 (unit μm) can be referred to the values ​​in Table 2 below:

[0109] Table 2j Value Quick Reference Table - Medium Wave Band 3.7~4.8 (unit: μm)

[0110]

[0111]

[0112] (a) The slope k is obtained by fitting the straight line.

[0113] The test was conducted using a mid-wave 640×512 cooled infrared focal plane detector, and the signal voltage V of the 16 pixels (at temperature T) at the center of the infrared focal plane was measured. out (T,t int ()), fitting signal voltage with integral time t int V out -t int Images (such as) Figure 2 ), obtain the slope k of the fitted line, and fill the fitted slope k into Table 4 of (b);

[0114] (b) Quantum efficiency

[0115] With the infrared focal plane detector output normal, check the value of the integrating capacitor C and the pixel area A in the detector readout circuit. d For example, taking the MM615S4S3-F4 detector as an example, the relevant parameter values ​​of the readout circuit are shown in Table 3:

[0116] Table 3. Parameters related to the detector readout circuit.

[0117] F number Integrating capacitor Pixel area 4 0.485pF <![CDATA[225μm 2 ]]>

[0118] Substitute the slope of the fitted line obtained in (a) and the relevant parameters of the infrared focal plane detector circuit in Table 3 into formula (7) to calculate the quantum efficiency of the central pixel of the detector at the corresponding temperature. The calculated values ​​of the quantum efficiency of the central pixel of the infrared focal plane detector at different temperatures are detailed in Table 4 below.

[0119] Table 4 shows the quantum efficiency values ​​of MM615S4S3-F4 in the room temperature range.

[0120]

[0121]

[0122] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included within the protection scope of the present invention.

Claims

1. A method for testing the quantum efficiency of an infrared focal plane detector, characterized in that, It includes an infrared focal plane detector and a black body that is aligned with the infrared focal plane detector and separated by a preset distance, so that the black body radiation uniformly illuminates the pixels of the infrared focal plane detector, and the black body operates at a preset temperature. And includes the following steps: Step S1: Obtain pixel voltage data of the infrared focal plane detector at different integration times; Step S2: Perform linear fitting on the pixel voltage data of the infrared focal plane detector with the integration time to determine the slope of the fitted line; Step S3: Obtain the optical F-number of the infrared focal plane detector, the integrating capacitance of the readout circuit on the infrared focal plane detector, the pixel area, and the Planck photon emissivity, and calculate the quantum efficiency by combining the slope of the determined fitted line.

2. The quantum efficiency testing method for an infrared focal plane detector according to claim 1, characterized in that, Step S1 includes: Obtain the output voltage of all pixels on the infrared focal plane detector; The output voltages of all pixels are averaged to obtain the pixel voltage data at different integration times.

3. The quantum efficiency testing method for an infrared focal plane detector according to claim 1, characterized in that, After step S3, the method further includes: Adjust the preset temperature, and measure and obtain the relationship between the pixel output voltage and the integration time after the preset temperature adjustment according to the process of steps S1-S3, so as to obtain the quantum efficiency at different blackbody temperatures.

4. The quantum efficiency testing method for an infrared focal plane detector according to claim 1, characterized in that, The quantum efficiency is calculated using the following formula: Where F represents the F-number of the optical interface of the infrared focal plane detector; n represents the compensation coefficient; k represents the slope of the fitted straight line; C represents the integrating capacitance of the readout circuit; j represents the Planck photon emissivity; A d η represents the pixel area; η represents the quantum efficiency.

5. The quantum efficiency testing method for an infrared focal plane detector according to claim 4, characterized in that, The Planck photon emissivity is determined using the following formula: Where λ represents the wavelength of the incident light radiated by the blackbody; h represents Planck's constant; c represents the speed of light in vacuum; T represents the preset temperature; K B denoted by Boltzmann constant; j represents the Planck photon emissivity.

6. The quantum efficiency testing method for an infrared focal plane detector according to claim 1, characterized in that, The preset temperature is 20℃-70℃.

7. The quantum efficiency testing method for an infrared focal plane detector according to claim 1, characterized in that, The infrared focal plane detector is a cooled infrared focal plane detector.

8. A quantum efficiency testing system for an infrared focal plane detector, characterized in that, A quantum efficiency testing method for implementing an infrared focal plane detector as described in any one of claims 1-7 includes an infrared focal plane detector and a black body that is aligned with the infrared focal plane detector and spaced apart by a preset distance, such that the black body radiation uniformly illuminates the pixels of the infrared focal plane detector, and the black body operates at a preset temperature. Also includes: The acquisition unit acquires pixel voltage data of the infrared focal plane detector at different integration times; The fitting processing unit, connected to the acquisition unit, performs linear fitting on the pixel voltage data of the infrared focal plane detector with the integration time to determine the slope of the fitting line. The calculation unit, connected to the fitting processing unit, obtains the optical F-number of the infrared focal plane detector, the integrating capacitance of the readout circuit on the infrared focal plane detector, the pixel area, and the Planck photon emissivity, and calculates the quantum efficiency by combining the slope of the determined fitting line.

9. The quantum efficiency testing system for an infrared focal plane detector according to claim 8, characterized in that, The acquisition unit specifically includes: The acquisition module acquires the output voltage of all pixels on the infrared focal plane detector; The processing module, connected to the acquisition module, averages the output voltage of all pixels to obtain the pixel voltage data at different integration times.

10. The quantum efficiency testing system for an infrared focal plane detector according to claim 8, characterized in that, Also includes: The adjustment unit adjusts the preset temperature to measure and obtain the relationship between the pixel output voltage and the integration time after the preset temperature adjustment, thereby obtaining the quantum efficiency at different blackbody temperatures.

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