A method and system for testing room temperature response parameters of infrared detectors

Abstract

The present invention relates to infrared light detection technology, and more specifically to a method and system for testing the room temperature response parameters of infrared detectors. The method aims to address the shortcomings of the prior art, such as the poor stability of the laser spot distribution in the mid-infrared band, the detector photosensitive surface being usually smaller than the laser spot, resulting in inaccurate test and calibration results of response parameters such as the detector saturation threshold, and large measurement error. The method for testing the room temperature response parameters of an infrared detector of the present invention comprises the following steps: combining an AC light signal and a DC light signal to form a combined light signal, controlling the combined light signal to irradiate the photosensitive surface of the detector under test, extracting the AC signal output by the detector under test and measuring its corresponding voltage value, recording the minimum and maximum optical power values ​​of the DC light signal, calculating the corresponding optical power density, obtaining the linear dynamic range and saturation threshold of the detector under test, and calculating the response rate of the detector under test.

Description

Technical Field

[0001] The present invention relates to infrared light detection technology, and in particular to a method and system for testing room temperature response parameters of an infrared detector. Background Art

[0002] With the development and application of laser technology, infrared laser detection technology has rapidly expanded. Near-infrared and mid-infrared detectors are widely used in the field of photoelectric detection in their respective wavelength bands. One of the main uses of infrared laser detection technology is laser parameter testing. In large-area, multi-faceted array detection systems or devices, infrared detectors are arranged in a dot matrix, and through photoelectric signal conversion, parameters such as the power density distribution of the measured laser spot, the size of the ring, and the total incident power can be tested. Therefore, accurately measuring parameters such as the room temperature responsivity, saturation threshold, and linear dynamic range of infrared detectors directly determines the application range of laser parameter testing equipment and the accuracy of test results.

[0003] At present, domestic and international standards have stipulated the test methods for infrared detector blackbody response rate, relative spectral response, impedance and other parameters. However, there are no relevant standards for the response parameter of infrared detection device saturation threshold, nor are there standardized verification and test methods. In the process of developing laser detection and test equipment, the principle of the test system is as follows: Figure 1 As shown, the device includes a laser 101, an optical chopper 102 arranged along the laser's output optical path, a detector 103, and a lock-in amplifier 104 connected to the detector 103. A commonly used calibration and testing method for the detector's saturation threshold is to use a laser as a calibration light source, testing and calibrating the detector's saturation threshold and linear dynamic range by increasing the output power from low to high. However, some lasers have poor output power and spot distribution stability, especially for mid-infrared lasers. Their poor beam quality leads to poor spot distribution stability, and the detector's photosensitivity surface is typically smaller than the laser spot. Consequently, the test and calibration results for response parameters such as the detector's saturation threshold are inaccurate, resulting in large measurement errors. Summary of the Invention

[0004] The purpose of the present invention is to solve the shortcomings in the prior art of poor stability of laser spot distribution in the mid-infrared band, the detector photosensitive surface is usually smaller than the laser spot, resulting in inaccurate test and calibration results of response parameters such as the detector saturation threshold, and large errors in measurement results, and to provide a method and system for testing the room temperature response parameters of infrared detectors.

[0005] Inventive concept

[0006] Room temperature response parameters include room temperature response rate, saturation threshold, and linear dynamic range.

[0007] An AC optical signal and a DC optical signal are used to form a combined beam. This combined beam is then irradiated onto the photosensitive surface of the detector under test. The output signal of the detector under test now includes both an AC signal generated by the AC optical signal and a DC signal generated by the DC optical signal. The AC signal output by the detector under test is then extracted. During the experiment, the AC optical signal remains constant, while the DC optical power varies from low to high. When the combined beam received by the detector under test is below the saturation threshold, the extracted AC signal remains essentially constant. As the DC optical power output by the laser gradually increases, the detector under test gradually approaches saturation. When the AC signal output by the detector under test begins to decrease from a constant value, it indicates that the detector under test has begun to saturate. The maximum DC optical power reached before the AC signal output by the detector under test decreases is the incident optical power at which the detector under test saturates. The saturation threshold is calculated based on the area of ​​the detector's photosensitive surface and the incident optical power at saturation. The optical power density range corresponding to the minimum and maximum values ​​when the laser output DC optical power changes from low to high is the linear dynamic range of the detector under test. The ratio of the output voltage value of the detector under test when working within the linear dynamic range to the optical power density of the corresponding AC optical signal is the response rate of the detector under test.

[0008] To achieve the above objectives, the present invention provides the following technical solutions:

[0009] A method for testing room temperature response parameters of an infrared detector is characterized in that it comprises the following steps:

[0010] Step 1: Combine the AC optical signal and the DC optical signal to form a combined optical signal, and control the combined optical signal to irradiate the photosensitive surface of the detector under test;

[0011] The AC optical signal is a stable value;

[0012] Step 2: The detector under test outputs corresponding AC and DC signals, extracts the AC signal, and measures its corresponding voltage value;

[0013] Step 3: Record the minimum and maximum optical power values ​​of the DC optical signal;

[0014] The optical power of the DC optical signal is controlled to increase from low to high until the voltage value of the AC signal output by the detector under test begins to decrease from a constant value;

[0015] The maximum value of the DC optical signal's optical power before the AC signal voltage drops is the saturation value of the incident optical power of the detector under test. The minimum value of the DC optical signal's optical power is determined by the sensitivity of the detector under test.

[0016] Step 4: Calculate the corresponding optical power density according to the minimum and maximum optical power values ​​of the DC optical signal, and record them as the first optical power density and the second optical power density respectively;

[0017] The range from the first optical power density to the second optical power density is the linear dynamic range of the detector under test; the second optical power density is the saturation threshold of the detector under test;

[0018] Step 5: Calculate the response rate of the detector under test based on the voltage value of the AC electrical signal output by the detector under test and the optical power density of the corresponding AC optical signal.

[0019] Furthermore, in step 5, the response rate of the detector under test is calculated by the following formula:

[0020]

[0021] Where R is the response rate, U is the voltage value of the AC signal output by the detector under test, and S2 is the optical power density of the AC optical signal.

[0022] Furthermore, in step 1, the AC light signal is generated specifically as follows: the radiation light generated by the high-temperature blackbody radiation source is modulated by an optical chopper to form the AC light signal.

[0023] Furthermore, the temperature resolution of the high-temperature blackbody radiation source is 0.1°C, the effective emissivity is greater than or equal to 0.99, and the calibration accuracy is 0.2°C.

[0024] Furthermore, in step 4, the optical power density of the DC optical signal is calculated by the following formula:

[0025]

[0026] Where S1 is the optical power density of the DC optical signal, P is the output DC optical power, which is obtained through actual measurement; A D is the photosensitive surface area of ​​the detector under test.

[0027] At the same time, a system for implementing the above-mentioned infrared detector room temperature response parameter testing method is also provided, which is special in that: it includes an AC light emitting device, a DC light emitting device, a beam combiner and an AC signal receiving device; the optical axes of the AC light signal emitted by the AC light emitting device and the DC light signal emitted by the DC light emitting device are arranged vertically; the beam combiner is arranged at the intersection of the AC light signal and the DC light signal; the detector to be tested is arranged on the combined light path of the beam combiner, and the combined light of the beam combiner is irradiated on the photosensitive surface of the detector to be tested, and the input end of the AC signal receiving device is used to connect the output end of the detector to be tested; the beam combiner is used to transmit the AC light signal and reflect the DC light signal to form a combined light.

[0028] Furthermore, the AC light emitting device includes a high-temperature blackbody radiation source and a narrow-band filter and an optical chopper sequentially arranged along the radiation light path of the high-temperature blackbody radiation source;

[0029] The DC light emitting device includes a laser;

[0030] The AC signal receiving device is a lock-in amplifier;

[0031] The transmittance of the beam combiner to the AC light signal and the reflectance of the DC signal are both greater than or equal to 50%.

[0032] Furthermore, the beam combiner has a transmission-reflection ratio of 1:1.

[0033] Furthermore, the distance between the photosensitive surface of the detector under test and the blade surface of the optical chopper is greater than 10 times the cavity diameter of the high-temperature blackbody radiation source.

[0034] Furthermore, an aperture assembly is provided at the output end of the high-temperature blackbody radiation source;

[0035] The output end of the laser is provided with an attenuation plate.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The present invention utilizes stable and uniform AC light signals and DC light signals to simultaneously irradiate the photosensitive surface of the detector under test. During measurement, the electrical signal output by the blackbody radiation light signal after passing through the detector under test is extracted. The AC light emitting device preferably uses a high-temperature blackbody radiation source. The light signal radiated by the high-temperature blackbody radiation source is more stable than the light signal output by any laser, eliminating the influence of the instability of the DC laser output light signal. Therefore, the accuracy of the measurement results of the detection response parameters is greatly improved compared with the existing technology, and the measurement uncertainty of the detector response parameters is greatly reduced.

[0038] 2. The present invention can be used to test and calibrate the room temperature response parameters of detectors at any narrowband single wavelength. Since blackbody radiation is broadband radiation, stable measurement of any wavelength can be achieved by selecting the corresponding narrowband filter according to the measurement wavelength.

[0039] 3. The technical route provided by the present invention can realize the simultaneous measurement of the detector's room temperature response rate, saturation threshold, and linear dynamic range using the same optical path.

[0040] 4. The present invention realizes the room temperature response rate, saturation threshold and linear dynamic range testing and calibration of detectors in the visible light, near infrared and mid-infrared bands, and realizes the accurate measurement of the response parameters of detectors in a wide wavelength range. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the principle of saturation threshold test in the prior art;

[0042] Figure 2Schematic diagram of the principle of the test system in an embodiment of the present invention;

[0043] Figure 3 is the result curve measured in the embodiment of the present invention;

[0044] Description of reference numerals:

[0045] 101-laser, 102-optical chopper, 103-detector, 104-lock-in amplifier;

[0046] 201-high temperature blackbody radiation source, 202-aperture assembly, 203-narrowband filter, 204-optical chopper, 205-beam combiner, 206-detector under test, 207-locked amplifier, 208-laser. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] The infrared detector room temperature response parameter testing method of the present invention comprises the following steps:

[0049] Step 1: Combine the AC optical signal and the DC optical signal to form a combined optical signal, and control the combined optical signal to irradiate the photosensitive surface of the detector 206 under test;

[0050] Among them, the AC optical signal is a stable value and is emitted by a stable and uniform light source;

[0051] The light source in this embodiment is a high-temperature blackbody radiation source 201. An aperture assembly 202 is provided at the output end of the high-temperature blackbody radiation source 201 for adjusting the spot size of the radiated light to match the photosensitive surface of the detector 206 under test. The radiated light generated by the high-temperature blackbody radiation source 201 is modulated by an optical chopper 204 to form an AC light signal. A narrowband filter 203 is provided between the high-temperature blackbody radiation source 201 and the optical chopper 204 for adjusting the wavelength of the AC light signal. A DC light signal is emitted by a laser 208. The wavelengths of both the AC and DC light signals are determined by the detection wavelength of the detector 206 under test; the DC light signal has a fixed wavelength.

[0052] The high-temperature blackbody radiation source 201 has a temperature resolution of 0.1°C, an effective emissivity greater than or equal to 0.99, a calibration accuracy of 0.2°C, and is traceable to NIST (National Bureau of Weights and Measures).

[0053] Step 2: The detector under test 206 outputs corresponding AC and DC signals, extracts the AC signal, and measures the corresponding voltage value;

[0054] In this embodiment, a lock-in amplifier 207 is used to measure the voltage value of the AC signal;

[0055] Step 3: Record the minimum and maximum optical power values ​​of the DC optical signal;

[0056] The optical power of the DC optical signal is controlled to increase from low to high until the voltage value of the AC signal output by the measured detector 206 starts to decrease from a constant value. The optical power of the DC optical signal and its corresponding voltage value of the AC signal are recorded to obtain a corresponding curve, such as Figure 3 , which is the measurement result of this embodiment, the horizontal axis in the figure is the optical power of the DC optical signal, and the vertical axis is the voltage value of the corresponding AC signal.

[0057] The maximum value of the optical power of the DC optical signal before the voltage value of the AC signal drops is the saturation value of the incident optical power of the detector 206 under test, corresponding to Figure 3 At point A in FIG, according to the sensitivity of the detector 206 under test, the minimum optical power value that can be measured is the minimum value of the DC optical signal power.

[0058] Step 4: Calculate the corresponding optical power density according to the minimum and maximum optical power values ​​of the DC optical signal, and record them as the first optical power density and the second optical power density respectively;

[0059] The range from the first optical power density to the second optical power density is the linear dynamic range of the detector 206 under test; the second optical power density is the saturation threshold of the detector 206 under test;

[0060] The optical power density of the DC optical signal is calculated by the following formula:

[0061]

[0062] Wherein, S1 is the optical power density of the DC optical signal, P is the DC optical power output by the laser 208, which is obtained through actual measurement; A D is the photosensitive surface area of ​​the detector 206 under test;

[0063] Step 5: Calculate the response rate of the detector 206 under test using the following formula:

[0064]

[0065] Wherein, R is the response rate, U is the voltage value of the AC signal output by the detector 206 under test, and S2 is the optical power density of the AC optical signal.

[0066] The optical power density calculation method of AC optical signal is as follows:

[0067] During the room temperature responsivity, saturation threshold, and linear dynamic range tests of the detector 206 under test, the radiation amount of the high-temperature blackbody radiation source 201 is the power value radiated per unit area into a 2π space within a unit wavelength interval, and is calculated using the Planck blackbody radiation formula, which is as follows:

[0068]

[0069] Among them, M bλ is the spectral radiation of the black body (W·m·μm -1 ), λ is the measurement wavelength (μm), T is the blackbody temperature (K), k is the Boltzmann constant, c1 is the first radiation constant, and c2 is the second radiation constant.

[0070] During the response parameter test of the detector 206 at a single wavelength, since the narrowband filter 203 is provided, the radiation amount of the high-temperature blackbody radiation source 201 received by the detector 206 is the power within a wavelength range Δλ. Generally, the transmittance of different wavelengths within the Δλ range is different. Therefore, when applying the Planck blackbody radiation formula to calculate the light radiation amount of the detector's photosensitive surface, the spectral transmittance curve of the filter should be integrated within the bounded region λ1 to λ2 to obtain the radiance within the λ1 to λ2 band, which can be expressed as:

[0071]

[0072] Among them, M b,T,λ1～λ2 is the radiance in the λ1~λ2 band, T λ is the transmittance of the narrowband filter 203 at wavelength λ.

[0073] The optical power density per unit area of ​​the detector radiated by the high-temperature blackbody radiation source 201 is calculated by the following formula:

[0074]

[0075] Wherein, S2 is the optical power density per unit area of ​​the detector 206 radiated by the high temperature black body radiation source 201, that is, the optical power density of the AC optical signal, C rms is the energy root mean square conversion coefficient of the modulated radiation light of the high-temperature blackbody radiation source 201, which is obtained by looking up the table, ε is the effective emissivity of the high-temperature blackbody radiation source 201, A is the area of ​​the light aperture of the aperture assembly 202, and L is the distance between the aperture assembly 202 and the photosensitive surface of the detector 206 under test.

[0076] The infrared detector room temperature response parameter testing system of the present invention includes a high-temperature blackbody radiation source 201, a narrowband filter 203 and an optical chopper 204 arranged in sequence along the radiation path of the high-temperature blackbody radiation source 201, a laser 208 arranged perpendicular to the radiation path of the high-temperature blackbody radiation source 201, a beam combiner 205, and a lock-in amplifier 207. The high-temperature blackbody radiation source 201 is a stable and uniform light source. After the wavelength of the radiated light is selected by the narrowband filter 203, it is modulated by the optical chopper 204 to form an AC light signal. The beam combiner 205 is arranged at the intersection of the AC light signal and the DC light signal emitted by the laser 208, and transmits and reflects them respectively to form a combined light beam. The lock-in amplifier 207 is arranged on the combined light path.

[0077] like Figure 2 As shown, during use, the detector under test 206 is positioned in the combined optical path between the beam combiner 205 and the lock-in amplifier 207. The detector under test 206 should be equipped with a preamplifier that enables normal operation. The combined light beam is irradiated onto the photosensitive surface of the detector under test 206. The detector under test 206 receives the combined light beam and performs photoelectric conversion to output an electrical signal, which includes a DC signal and an AC signal. The lock-in amplifier 207 is used to extract the AC signal. The photosensitive surface of the detector under test 206 is coaxial with the combined optical path. The distance between the photosensitive surface of the detector under test 206 and the blade surface of the optical chopper 204 is greater than 10 times the cavity diameter of the high-temperature blackbody radiation source 201. The blackbody radiation is treated as a point light source to improve measurement accuracy.

[0078] Among them, the temperature control accuracy of the high-temperature blackbody radiation source 201 is as low as 0.2°C, ensuring that the AC light signal modulated by the optical chopper 204 is stable and uniform; the high-temperature blackbody radiation source 201 is provided with an adjustable aperture assembly 202. By adjusting the aperture assembly 202, different apertures can be selected to adjust the spot size of the radiated light. In the experiment, the appropriate aperture is selected according to the size of the photosensitivity surface of the detector 206 under test, so that the spot of the radiated light is adapted to the size of the photosensitivity surface; the chopping frequency of the optical chopper 204 needs to avoid the resonant frequency of the circuit; at the measurement wavelength, the transmittance-reflection ratio of the beam combiner 205 is as close to 1:1 as possible, and the transmittance of the AC light signal and the reflectance of the DC signal are both greater than or equal to 50%.

[0079] In other embodiments of the present invention, an attenuation plate is further provided on the outgoing light path of the laser 208 to reduce the intensity of the outgoing light of the laser 208 .

[0080] The method of using the test system includes the following steps:

[0081] S1, build a test system and select a suitable aperture according to the size of the photosensitive surface of the detector 206 under test;

[0082] S2, the radiation light from the high-temperature blackbody radiation source 201 is incident on the narrowband filter 203 through the aperture for wavelength selection. The center wavelength and bandwidth of the narrowband filter 203 are selected according to the measurement requirements of the detector 206 under test;

[0083] S3, after the radiated light passes through the narrowband filter 203, it enters the optical chopper 204, where it is modulated to form an AC optical signal. During the experiment, a suitable chopping frequency can be set to avoid the influence of the same-frequency vibration of the circuit;

[0084] S4, the AC light signal is transmitted by the beam combiner 205. At the same time, the DC light signal output by the laser 208 is reflected by the beam combiner 205. The transmitted light and the reflected light of the beam combiner 205 form a combined light beam that irradiates the photosensitive surface of the detector 206 under test. The detector 206 under test outputs a DC signal and an AC signal.

[0085] The wavelength and power of the laser 208 are selected according to the requirements of the detector 206 under test. In the experiment, a laser 208 with a fixed wavelength is preferred;

[0086] S5 , the lock-in amplifier 207 receives the AC signal output by the detector 206 under test, and obtains the output voltage value of the detector 206 under test.

Claims

1. A method for testing room temperature response parameters of an infrared detector, characterized in that: An infrared detector room temperature response parameter testing system is used, wherein the infrared detector room temperature response parameter testing system comprises an AC light emitting device, a DC light emitting device, a beam combining mirror (205) and an AC signal receiving device; The optical axes of the AC light signal emitted by the AC light emitting device and the DC light signal emitted by the DC light emitting device are arranged vertically; The beam combining mirror (205) is arranged at the intersection of the AC optical signal and the DC optical signal; The detector (206) to be measured is arranged on the combined light path of the beam combining mirror (205), the combined light of the beam combining mirror (205) is irradiated on the photosensitive surface of the detector (206) to be measured, and the input end of the AC signal receiving device is connected to the output end of the detector (206) to be measured; The beam combining mirror (205) is used to transmit the AC optical signal and reflect the DC optical signal to form a combined beam; The AC light emitting device comprises a high-temperature blackbody radiation source (201), and a narrowband filter (203) and an optical chopper (204) sequentially arranged along a radiation light path of the high-temperature blackbody radiation source (201); The DC light emitting device includes a laser (208); The AC signal receiving device is a lock-in amplifier (207); The transmittance of the beam combiner (205) to the AC light signal and the reflectance of the DC signal are both greater than or equal to 50%; The test method includes the following steps: Step 1, combining an AC optical signal and a DC optical signal to form a combined optical signal, and controlling the combined optical signal to irradiate the photosensitive surface of the detector (206) under test; The AC optical signal is a stable value; Step 2: the detector under test (206) outputs corresponding AC and DC signals, extracts the AC signal, and measures its corresponding voltage value; Step 3: Record the minimum and maximum optical power values ​​of the DC optical signal; Controlling the optical power of the DC optical signal to increase from low to high until the voltage value of the AC electrical signal output by the detector (206) under test starts to decrease from a constant value; The maximum value of the optical power of the DC optical signal before the voltage value of the AC signal drops is the saturation value of the incident optical power of the detector under test (206), and the minimum value of the optical power of the DC optical signal is determined by the sensitivity of the detector under test (206); Step 4: Calculate the corresponding optical power density according to the minimum and maximum optical power values ​​of the DC optical signal, and record them as the first optical power density and the second optical power density respectively; The range from the first optical power density to the second optical power density is the linear dynamic range of the detector (206) under test; the second optical power density is the saturation threshold of the detector (206) under test; Step 5: Calculate the response rate of the detector (206) under test based on the voltage value of the AC electrical signal output by the detector (206) under test and the optical power density of the corresponding AC optical signal.

2. The method for testing room temperature response parameters of an infrared detector according to claim 1, wherein: In step 5, the response rate of the detector under test (206) is calculated by the following formula: Wherein, R is the response rate, U is the voltage value of the AC signal output by the detector (206) under test, and S2 is the optical power density of the AC optical signal.

3. The method for testing room temperature response parameters of an infrared detector according to claim 2, wherein: In step 1, the AC light signal is generated specifically as follows: the radiation light generated by the high-temperature blackbody radiation source (201) is modulated by the optical chopper (204) to form the AC light signal.

4. The method for testing room temperature response parameters of an infrared detector according to claim 3, wherein: The high-temperature blackbody radiation source (201) has a temperature resolution of 0.1°C, an effective emissivity greater than or equal to 0.99, and a calibration accuracy of 0.2°C.

5. A method for testing room temperature response parameters of an infrared detector according to any one of claims 1 to 4, characterized in that: In step 4, the optical power density of the DC optical signal is calculated using the following formula: Where S1 is the optical power density of the DC optical signal, P is the output DC optical power, which is obtained through actual measurement; A D is the photosensitive surface area of ​​the detector (206) under test.

6. The method for testing room temperature response parameters of an infrared detector according to claim 1, wherein: The beam combining mirror (205) has a transmission-reflection ratio of 1:

1.

7. The method for testing room temperature response parameters of an infrared detector according to claim 6, wherein: The distance between the photosensitive surface of the measured detector (206) and the blade surface of the optical chopper (204) is greater than 10 times the cavity diameter of the high-temperature blackbody radiation source (201).

8. The method for testing room temperature response parameters of an infrared detector according to claim 7, wherein: An aperture assembly (202) is provided at the output end of the high-temperature blackbody radiation source (201); The output end of the laser (208) is provided with an attenuation plate.

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