A method and system for testing the quantum efficiency of an infrared focal plane detector

Abstract

This invention provides a method and system for testing the quantum efficiency of an infrared focal plane detector, comprising a blackbody source aligned with and spaced at a preset distance from the infrared focal plane detector, such that blackbody radiation uniformly illuminates the infrared focal plane detector; the method includes: step S1, setting the temperature of the blackbody source to a first preset temperature and acquiring first pixel voltage data of the infrared focal plane detector at a preset integration time; step S2, setting the temperature to a second preset temperature and acquiring second pixel voltage data of the infrared focal plane detector at the same preset integration time; step S3, calculating the pixel response voltage; and step S4, acquiring the F-number, integrating capacitance, pixel area, and Planck photon emissivity of the infrared focal plane detector, and calculating the quantum efficiency by combining the preset integration time and the calculated pixel response voltage. Beneficial effects: The testing method is simple, data acquisition is convenient, and data processing is straightforward.

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 of a surface source that is aligned with the infrared focal plane detector and set at a preset distance, such that the black body radiation is uniformly irradiated onto the infrared focal plane detector.

[0008] And includes the following steps:

[0009] Step S1: Set the surface source blackbody temperature to a first preset temperature and obtain the first pixel voltage data of the infrared focal plane detector at a preset integration time.

[0010] Step S2: Set the surface source blackbody temperature to a second preset temperature, and obtain the second pixel voltage data of the infrared focal plane detector at the same preset integration time.

[0011] Step S3: Calculate the pixel response voltage between the first preset temperature and the second preset temperature based on the first pixel voltage data and the second pixel voltage data;

[0012] Step S4: Obtain the F-number of the optics 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 preset integration time and the calculated pixel response voltage.

[0013] Preferably, step S3 specifically includes:

[0014] The pixel response voltage is obtained by performing a difference processing on the first pixel voltage data and the second pixel voltage data.

[0015] Preferably, after step S4, the method further includes:

[0016] Adjust the first preset temperature and the second preset temperature, and measure the corresponding pixel response voltage after temperature adjustment under the same integration time according to the process of steps S1-S4, so as to obtain the quantum efficiency at different blackbody temperatures.

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

[0018]

[0019] Where F represents the F-number of the infrared focal plane detector; n represents the compensation coefficient; K represents the gain; C represents the integrating capacitance of the readout circuit; j-j0 represents the difference in Planck photon emissivity at the first preset temperature and the second preset temperature; A d t represents the area of ​​the pixel; int η represents the preset integration time; 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 a surface source 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.

[0026] Also includes:

[0027] The first acquisition unit is used to set the surface source blackbody temperature to a first preset temperature and acquire the pixel voltage data of the infrared focal plane detector under a preset integration time.

[0028] The second acquisition unit is used to set the surface source blackbody temperature to a second preset temperature and acquire the pixel voltage data of the infrared focal plane detector under the same preset integration time.

[0029] The processing unit is connected to the first acquisition unit and the second acquisition unit respectively, and is used to calculate the pixel response voltage between the first preset temperature and the second preset temperature based on the first pixel voltage data and the second pixel voltage data.

[0030] The computing unit, connected to the processing unit, is used to obtain the F-number of the optics 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 preset integration time and the calculated pixel response voltage.

[0031] Preferably, the processing unit specifically includes:

[0032] The difference processing module is used to perform difference processing on the first pixel voltage data and the second pixel voltage data to obtain the pixel response voltage.

[0033] Preferably, it further includes:

[0034] An adjustment unit is used to adjust the first preset temperature and the second preset temperature to measure the pixel response voltage corresponding to the temperature adjustment under the same integration time, 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 testing method of this invention is simple and feasible, and data acquisition and processing are convenient. Attached Figure Description

[0037] Figure 1This 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 output voltage with the temperature of the blackbody source 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 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 a surface source aligned with the infrared focal plane detector and set at a preset distance, so that the black body radiation is uniformly irradiated on the infrared focal plane.

[0043] And includes the following steps:

[0044] Step S1: Set the surface source blackbody temperature to a first preset temperature and acquire the first pixel voltage data of the infrared focal plane detector at a preset integration time.

[0045] Step S2: Set the surface source blackbody temperature to a second preset temperature and acquire the second pixel voltage data of the infrared focal plane detector at the same preset integration time.

[0046] Step S3: Calculate the pixel response voltage between the first preset temperature and the second preset temperature based on the first pixel voltage data and the second pixel voltage data;

[0047] Step S4: Obtain the F-number of the optics 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 preset integration time and the calculated pixel response voltage.

[0048] In a preferred embodiment, step S3 specifically includes:

[0049] The pixel response voltage is obtained by subtracting the voltage data of the first pixel and the voltage data of the second pixel.

[0050] In a preferred embodiment, after step S4, the method further includes:

[0051] Adjust the first preset temperature and the second preset temperature, and measure the corresponding pixel response voltage after temperature adjustment under the same integration time conditions according to the process of steps S1-S4, 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 F-number of the infrared focal plane detector; n represents the compensation coefficient; K represents the gain; C represents the integrating capacitance of the readout circuit; j-j0 represents the difference in Planck photon emissivity at the first and second preset temperatures; Ad represents the pixel area; t int η represents the preset integration time; 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 from the blackbody radiation; 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 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 of a surface source aligned with the infrared focal plane detector and set at a preset distance, such that the black body radiation is uniformly irradiated onto the pixels of the infrared focal plane detector.

[0061] Also includes:

[0062] The first acquisition unit is used to set the surface source blackbody temperature to a first preset temperature and acquire the pixel voltage data of the infrared focal plane detector under a preset integration time.

[0063] The second acquisition unit is used to set the surface source blackbody temperature to a second preset temperature and acquire the pixel voltage data of the infrared focal plane detector at the same preset integration time.

[0064] The processing unit is connected to the first acquisition unit and the second acquisition unit respectively, and is used to calculate the pixel response voltage between the first preset temperature and the second preset temperature based on the first pixel voltage data and the second pixel voltage data.

[0065] The computing unit, connected to the processing unit, is used to obtain the F-number of the optics 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 preset integration time and the calculated pixel response voltage.

[0066] In a preferred embodiment, the processing unit specifically includes:

[0067] The difference processing module is used to perform difference processing on the first pixel voltage data and the second pixel voltage data to obtain the pixel response voltage.

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

[0069] The adjustment unit is used to adjust the first preset temperature and the second preset temperature to measure the quantum efficiency corresponding to the temperature adjustment, thereby obtaining the quantum efficiency at different blackbody temperatures.

[0070] Furthermore, this embodiment of the invention provides a simple and feasible method for testing the quantum efficiency of an MCT cooled infrared focal plane detector. Data acquisition is convenient, and the calculation can be performed directly using the pixel response voltage data acquired according to national standards. It is suitable for focal plane detectors with relatively small dark current.

[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 an 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;

[0077] 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;

[0078] A d This represents the pixel area of ​​a single pixel at the center of an infrared focal plane detector.

[0079] η represents quantum efficiency (i.e., the number of electron-hole pairs produced by each incident photon);

[0080] j represents the Planck photon emissivity of light per square micrometer per second (radiation band λ1~λ2, the spectral response range of the infrared focal plane array, in μm) when the temperature of the thermal radiation source (or blackbody) directly opposite the infrared focal plane detector is T. The unit is ph / (μm). 2 ·s);

[0081] According to radiometry, the Planck photon emissivity j is given by the following formula:

[0082]

[0083] Where λ represents the wavelength of the incident photon (unit: μm);

[0084] h represents Planck's constant, h = 6.626 × 10⁻⁶ -34 J.s;

[0085] c represents the speed of light in a vacuum, c = 3.0 × 10⁻⁶ 14 μm / s;

[0086] k B K represents the Boltzmann constant. B = I.38065×10 -23 J / K;

[0087] These physical quantities take the following values ​​during calculation:

[0088] As can be seen from Equation (3), when the temperature T of the thermal radiation source is stable and the distance r from the infrared focal plane detector to the thermal radiation source remains unchanged, the radiation photon flux density received by the infrared focal plane within the wavelength range between λ1 and λ2 (unit: μm) is constant. The calculation formula for the radiation photon flux density is:

[0089]

[0090] It can be seen that the number of photons received per square micron on a specific pixel of the infrared focal plane per unit time is constant. That is, the number of electron-hole pairs generated per square micron on this pixel per unit time is constant, which means that the quantum efficiency of the infrared focal plane is a stable value. When the temperature T changes, the quantum efficiency of the infrared focal plane will change slightly. Usually, the change is not large. Assume that when the target temperature is between T0 and T (T0 < T), the quantum efficiency of the infrared focal plane remains stable. The quantum efficiency is represented by η. Then, when the blackbody temperature is T, the signal voltage output value V out (T) satisfies the following relationship:

[0091]

[0092] When the blackbody temperature is T0, the signal voltage output value V out (T0) is

[0093]

[0094] Combined with GB / T 17444-2013, the pixel response voltage V s is

[0095]

[0096] In the formula, K represents the gain, which is the amplification factor of the amplifier in the test;

[0097] Combined with the infrared focal plane parameter test method in GB / T 17444-2013, it can be known that the radiation photon flux density incident on the pixel can be obtained by the following formula during approximate calculation:

[0098]

[0099] When F > 1, n takes the value of 1; when F ≤ 1, n takes the value of 0. Substitute the above formula into Equation (7). Therefore, when the blackbody temperature changes between T0 and T (T0 < T), the pixel response voltage of the infrared focal plane can also be expressed as

[0100]

[0101] Then the quantum efficiency η is

[0102]

[0103] According to the infrared focal plane parameter test method of GB / T 17444-2013, the response voltage V s can be directly calculated from the actual test values according to formula (6). When V s becomes a known quantity and is substituted into formula (8), the quantum efficiency of the focal plane can be calculated when the target temperatures are T0 to T (T0 < T).

[0104] The method for testing the quantum efficiency of the present invention can be attributed to the test of the signal voltage at different blackbody temperatures and the same integration time, that is, when the integration time is the same, the response voltage V of the infrared focal plane detector is measured under the change of the blackbody temperature from T0 to T (T0 < T). s After the response voltage is measured, the quantum efficiency of the infrared focal plane detector can be calculated according to formula (8) derived above.

[0105] The infrared focal plane (IRFPA) in the embodiment of the present invention is a detector sensitive to infrared irradiation and a device with a readout circuit. During the test, the infrared focal plane is aligned with the area source blackbody through an optical system, and a bias voltage and a working pulse are provided to the infrared focal plane through a control module to ensure its normal operation, and the collected signals are subjected to signal processing and data acquisition processing and then sent to the control module, and the control module interacts with the computer.

[0106] (1) Test conditions:

[0107] 1.1 The blackbody temperature is stable, the original image is output and the output is not modulated;

[0108] 1.2 The blackbody radiation should ensure uniform irradiation of each pixel of the focal plane;

[0109] 1.3 When testing the area source blackbody, the recommended blackbody temperatures are 20°C, 30°C, 40°C, 50°C, 60°C, and 70°C;

[0110] (2) The test steps are as follows:

[0111] 2.1 Connect the test system according to the test block diagram and prefabricate the test system;

[0112] 2.2 Adjust the test system, apply the optimal bias voltage to the cooled infrared focal plane detector to make the detector in a normal working state;

[0113] 2.3 At blackbody temperatures of 20°C, 30°C, 40°C, 50°C, 60°C, and 70°C respectively, keep the integration time unchanged through the serial port tool, and collect 100 frames of data at each blackbody temperature, and a set of two-dimensional arrays V out [(i,j),T,tint ;

[0114] 2.4 Measure a two-dimensional array at adjacent temperatures and the same integration time. After calculating the pixel response voltage between the two temperatures, the quantum efficiency η between the two temperatures can be calculated according to the formula derived above.

[0115] (3) Data acquisition and processing:

[0116] 3.1 At room temperature, a set of two-dimensional data V is collected respectively when the blackbody temperatures are 20°C, 30°C, 40°C, 50°C, 60°C, and 70°C and the integration time remains unchanged out [(i, j), T, t int

[0117] 3.2 Find 16 pixels (or 9 pixels) at the center of the infrared focal plane, and average their output voltages to obtain the pixel signal voltage data V at the same integration time under different temperatures out (T, t int ).

[0118] 3.3 Substitute the response voltage V of the infrared focal plane detector at T0 to T (T0 < T) s into formula (8) to calculate the quantum slope η of the detector, where C is given by the integration capacitance of the readout circuit, and A d is given by the pixel specification parameters of the focal plane detector. Among them, j is obtained by integrating the spectral response band range λ1 to λ2 (unit: μm) of the infrared focal plane detector with the integral formula (3). Taking the refrigerated mid-wave infrared focal plane detector independently developed by Zhejiang Yuxin Microelectronics as an example, a type F4 infrared focal plane detector with the model number MM615S4S3 is used for relevant tests. Its spectral response range is 3.7 to 4.8 3.7 to 4.8 (unit: μm). The value of j in the mid-wave band of 3.7 to 4.8 (unit: μm) can refer to the values in Table 2:

[0119] Table 2 Quick reference table of j values - mid-wave band 3.7 to 4.8 (unit: μm)

[0120]

[0121] (a) Pixel response voltage V s

[0122] According to formula (6), the signal voltage V of the 16 pixels at the center of the infrared focal plane (at temperature T) out (T, t int ) minus the signal voltage V of the pixel (at temperature T0) out (T0, t int ) gives the response voltage V of the pixel sThe test was conducted using a 640×512 cooled infrared focal plane array detector developed by Zhejiang Juexin Microelectronics. The output voltage of the 16 pixels at the center of the array at various temperatures is shown in the graph below. Figure 2 At the same time, according to Figure 2 The response voltage V in different temperature ranges was calculated from the raw data. s And fill the calculated response voltage into Table 4 of (b);

[0123] (b) Quantum efficiency

[0124] 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 cooled infrared detector independently developed by Zhejiang Juexin Microelectronics as an example, the relevant parameter values ​​of the readout circuit are shown in Table 3:

[0125] Table 3. Parameters related to the detector readout circuit.

[0126]

[0127]

[0128] The response voltage V in (a) s Substituting the relevant parameters of the infrared focal plane detector readout circuit in Table 3 into formula (8) for calculation, the quantum efficiency of the infrared focal plane detector can be obtained. The calculated values ​​of quantum efficiency in different temperature ranges are detailed in Table 4 below.

[0129] Table 4 shows the quantum efficiency values ​​of MM615S4S3-F4 in the room temperature range.

[0130]

[0131] 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 is uniformly irradiated onto the infrared focal plane detector. And includes the following steps: Step S1: Set the surface source blackbody temperature to a first preset temperature and obtain the first pixel voltage data of the infrared focal plane detector at a preset integration time. Step S2: Set the surface source blackbody temperature to a second preset temperature, and obtain the second pixel voltage data of the infrared focal plane detector at the same preset integration time. Step S3: Calculate the pixel response voltage between the first preset temperature and the second preset temperature based on the first pixel voltage data and the second pixel voltage data; Step S4: Obtain the F-number of the optical interface 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 preset integration time and the calculated pixel response voltage. The quantum efficiency is calculated using the following formula: ； Wherein, F represents the F-number of the optical interface of the infrared focal plane detector; n represents the compensation coefficient; K represents the gain; Vs represents the pixel response voltage; C represents the integrating capacitance of the readout circuit; j-j0 represents the difference in Planck photon emissivity at the first preset temperature and the second preset temperature; A d t represents the area of ​​the pixel; int η represents the preset integration time; η represents the quantum efficiency.

2. The quantum efficiency testing method for an infrared focal plane detector according to claim 1, characterized in that, Step S3 specifically includes: The pixel response voltage is obtained by performing a difference processing on the first pixel voltage data and the second pixel voltage data.

3. The quantum efficiency testing method for an infrared focal plane detector according to claim 1, characterized in that, After step S4, the method further includes: Adjust the first preset temperature and the second preset temperature, and measure the corresponding pixel response voltage after temperature adjustment under the same integration time according to the process of steps S1-S4, 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 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.

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

6. 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.

7. 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 1-6 includes an infrared focal plane detector and a black body of a surface source aligned with the infrared focal plane detector and spaced apart by a preset distance, such that the black body radiation uniformly illuminates the infrared focal plane detector. Also includes: The first acquisition unit is used to set the surface source blackbody temperature to a first preset temperature and acquire the pixel voltage data of the infrared focal plane detector under a preset integration time. The second acquisition unit is used to set the surface source blackbody temperature to a second preset temperature and acquire the pixel voltage data of the infrared focal plane detector under the same preset integration time. The processing unit is connected to the first acquisition unit and the second acquisition unit respectively, and is used to calculate the pixel response voltage between the first preset temperature and the second preset temperature based on the first pixel voltage data and the second pixel voltage data. The computing unit, connected to the processing unit, is used to obtain the F-number of the optical interface 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 preset integration time and the calculated pixel response voltage.

8. The quantum efficiency testing system for an infrared focal plane detector according to claim 7, characterized in that, The processing unit specifically includes: The difference processing module is used to perform difference processing on the first pixel voltage data and the second pixel voltage data to obtain the pixel response voltage.

9. The quantum efficiency testing system for an infrared focal plane detector according to claim 7, characterized in that, Also includes: An adjustment unit is used to adjust the first preset temperature and the second preset temperature to measure the pixel response voltage corresponding to the temperature adjustment under the same integration time, so as to obtain the quantum efficiency at different blackbody temperatures.

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