Calibration method and calibration device of high irradiance broadband radiometer

Abstract

The application discloses a calibration method and device of a wide-band irradiance meter with high irradiance. The method comprises the following steps: calibrating a spectral radiometric device to obtain a spectral correction coefficient; measuring spectral radiant flux of a fiber type wide-band light source and correcting the spectral radiant flux by using the spectral correction coefficient to obtain corrected spectral radiant flux; calculating radiant flux of a predetermined wave band according to the corrected spectral radiant flux; calculating a radiant illuminance value of a fiber output port as a standard value according to the radiant flux of the predetermined wave band; measuring a reading of a measured irradiance meter at the same fiber output port, comparing the reading with the standard value, and obtaining a calibration result. The application solves the problem that the existing light track method cannot be adapted to the fiber type irradiance meter by combining an integrating sphere with a standard fiber and introducing a fiber output light source into the integrating sphere to homogenize light. The radiant illuminance is accurately calculated by using a standard lamp calibration and a fiber end surface area, near distance measurement error is avoided, and accurate calibration of high irradiance is realized.

Description

Technical Field

[0001] This invention relates to the field of radiometric measurement technology, and in particular to a calibration method and calibration device for a high-radiance broadband radiometer. Background Technology

[0002] Broadband radiometers are commonly used in fields such as healthcare, photocatalysis, environmental monitoring, and material aging to measure the intensity of radiation from ultraviolet to visible light. Currently, two main calibration methods are employed: the optical track method, based on the inverse square law of distance, utilizes the principle that the irradiance produced by a point light source is inversely proportional to the square of the distance, obtaining different irradiance values ​​by adjusting the distance between the radiometer being calibrated and the standard light source; the integration sphere-based calibration method uses the highly reflective material on the inner wall of the integration sphere to create a uniform irradiance distribution, which can be used to calibrate fiber optic radiometers. Existing integration sphere calibration devices typically include a light source system, an integration sphere, a standard test port adapted to different fiber diameters, and an aperture assembly.

[0003] In the process of developing the existing technology, the inventors discovered that:

[0004] Fiber optic broadband radiometers use optical fibers directly connected to the light source output port, and their probe receives the light emitted from the fiber end face. This measurement method is fundamentally different from traditional free-space surface light sources such as metal halide lamps, xenon lamps, mercury lamps, and LED lamps.

[0005] The optical path method, based on the inverse square law of distance, requires the light source to be an ideal point source or a uniform surface source, and for the light to propagate in free space according to the spherical wave law. However, the output spot diameter and divergence angle of the optical fiber output end face are small, making it impossible to form a uniform illuminance field that conforms to the inverse square law at close range. To reproduce high irradiance on the order of W / cm², the distance between the fiber end face and the radiometer under test must be extremely close. At this distance, even slight non-uniformities of the light source itself can lead to serious errors. Therefore, the optical path method cannot be used to calibrate fiber optic broadband radiometers.

[0006] While existing calibration methods based on integrating spheres can be used for fiber optic radiometers, their design goal is to reproduce low irradiance in the μW / cm² to mW / cm² range. When attempting to reproduce high irradiance in the W / cm² range, they also face the problem of non-uniformity of direct light from the source. The integrating sphere typically lacks a homogenizing structure for high-power fiber input, resulting in insufficient uniformity of the optical field at the output, making it unsuitable as an accurate standard value. Furthermore, there is currently no comprehensive traceability chain for fiber optic broadband radiometers operating in high-irradiance scenarios, leading to significant differences in measurement results among laboratories and an expanded uncertainty (Urel) as high as 15%–48%, far exceeding the manufacturer's stated technical specifications of 5%–10%.

[0007] Therefore, this application provides a technical solution that enables accurate calibration of fiber optic broadband radiometers under high irradiance conditions to solve the problems in the prior art where the optical track method cannot be adapted to fiber optic radiometers, the integrating sphere method cannot reproduce high irradiance standard values, and there is a lack of dedicated calibration procedures. Summary of the Invention

[0008] To achieve accurate calibration of fiber optic broadband radiometers under high irradiance conditions, this application provides the following technical solution:

[0009] Specifically, the calibration method for a high-irradiance broadband radiometer includes the following steps:

[0010] Calibrate the spectral radiometry device and obtain the spectral correction coefficient;

[0011] The spectral radiant flux of the fiber-optic broadband light source is measured and corrected using the spectral correction coefficient to obtain the corrected spectral radiant flux.

[0012] Calculate the radiative flux of the predetermined band based on the corrected spectral radiative flux.

[0013] Calculate the irradiance value at the fiber optic output port based on the radiant flux of the predetermined band, and use it as the standard value.

[0014] The reading of the radiometer under test at the same fiber optic output port is measured, and the reading is compared with the standard value to obtain the calibration result;

[0015] The calibration result is a relative indication error or a correction factor.

[0016] Furthermore, the spectral correction coefficient is specifically as follows:

[0017] ;

[0018] Among them, the The standard spectral radiant flux is the standard spectral radiant flux of a standard lamp. The values ​​are measured by the spectral radiometry device for the standard lamp.

[0019] The further corrected spectral radiant flux is specifically as follows:

[0020] ;

[0021] Among them, the This represents the measured spectral radiant flux of a fiber-optic broadband light source using a spectral radiation measurement device.

[0022] Furthermore, the predetermined band is [ l 1, l 2], the predetermined band [ l 1, l The radiation flux of [2] is as follows:

[0023] .

[0024] Furthermore, the irradiance value is specifically:

[0025] ;

[0026] Where A is the area of ​​the fiber end face.

[0027] Furthermore, the spectral radiant flux of the standard lamp and the diameter of the standard optical fiber used to measure the fiber-optic broadband light source are both traceable to the measurement standard.

[0028] Furthermore, the reading of the radiometer under test is the average of at least three measurements.

[0029] Furthermore, the high irradiance refers to the irradiance at the output end face of the optical fiber being greater than or equal to 0.5 W / cm².

[0030] A high-irradiance broadband radiometer calibration device for implementing the above method includes:

[0031] An integrating sphere, which is provided with a light source input port, an output port and a calibration light source port, is used to provide a uniform diffuse reflection light field;

[0032] A spectral radiation measuring device is connected to the output port of the integrating sphere for measuring spectral radiant flux;

[0033] A spectral radiation flux standard lamp is installed at the calibration light source port of the integrating sphere to calibrate the spectral radiation measurement device;

[0034] At least one standard optical fiber is used to connect the fiber-optic broadband light source to the light source input port of the integrating sphere, so as to introduce the light source under test into the integrating sphere.

[0035] Furthermore, the integrating sphere is provided with several baffles, which are respectively located at the light source input port, output port, and calibration light source port.

[0036] Compared with existing technologies, this invention has the following advantages: By combining an integrating sphere with a standard optical fiber, a fiber-optic broadband light source is introduced into the integrating sphere for homogenization, providing a complete calibration process from calibration, measurement, correction to standard value calculation and indication comparison. This avoids the incompatibility of existing optical track methods with direct fiber output measurement, providing dedicated calibration for fiber-optic broadband radiometers. The spectral radiation measurement device is calibrated using a spectral radiation flux standard lamp, and the standard value of irradiance is accurately calculated based on the fiber end face area, avoiding close-range measurement errors and achieving accurate calibration for high irradiance. By utilizing a standard lamp and standard optical fiber traceable to the metrological reference, a complete metrological value transfer link is established from the metrological reference to the radiometer under test, solving the problems of incomplete traceability chains and large differences in measurement results between laboratories in existing systems. Attached Figure Description

[0037] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0038] Figure 1 A flowchart illustrating the calibration method for a high-irradiance broadband radiometer provided in this application embodiment.

[0039] Figure 2 This is a schematic diagram of the connection structure of a high-irradiance wide-band radiometer calibration device for implementing the method provided in an embodiment of this application.

[0040] Figure 3 This is a schematic diagram of the traceability structure for the measurement values ​​provided in an embodiment of this application.

[0041] Figure label:

[0042] Fiber optic broadband light source-1; Standard fiber optic cable-2; Standard fiber optic adapter-3; Integrating sphere-4; Baffle-5; Spectral radiant flux standard lamp-6; Power supply system for spectral radiant flux standard lamp-7; Spectral radiant measurement device-8. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0044] Please refer to Figure 1 The calibration method for a high-irradiance broadband radiometer provided in this application includes the following steps:

[0045] S101: Calibrate the spectral radiometry device to obtain the spectral correction coefficient.

[0046] Specifically, the steps for obtaining the spectral correction coefficients described above mainly include:

[0047] First, turn on the spectral radiant flux standard lamp installed at the calibration light source port of the integrating sphere for preheating;

[0048] After preheating, the spectral radiant flux of the output light is measured using a spectral radiance measurement device connected to the output port of the integrating sphere. ;

[0049] Spectral radiant flux based on a standard lamp with known spectral radiant flux , thus obtaining the spectral correction coefficient;

[0050] The spectral correction coefficient is specifically:

[0051] ;

[0052] Specifically, spectral correction coefficient This coefficient is used to reflect the measurement deviation of the spectral radiometry device in its current state, and subsequent measurements are corrected using this coefficient.

[0053] It should be noted that the spectral radiant flux of the output light is measured here. The spectral radiant flux of a standard lamp is known. The unit is W / nm, which is watts per nanometer. The spectral radiant flux of a standard lamp is known. Tracing back to the measurement standard, it can also be understood as the national standard.

[0054] S102: Measure the spectral radiant flux of the fiber-optic broadband light source and correct it with the spectral correction coefficient to obtain the corrected spectral radiant flux.

[0055] Specifically, before measuring the spectral radiant flux of a fiber-optic broadband light source, the spectral radiant flux standard lamp is turned off and allowed to cool down or until no light output is confirmed before measurement to avoid interference from the standard lamp's light in subsequent measurements. S102 specifically includes:

[0056] Illuminate the fiber-optic broadband light source connected to the light source input port of the integrating sphere via a standard optical fiber and an adapter.

[0057] The measured spectral radiant flux of the output light is measured by a spectral radiance measuring device connected to the output port of the integrating sphere. ;

[0058] Based on S101 spectral correction coefficient The corrected spectral radiant flux is obtained, wherein the corrected spectral radiant flux... Specifically:

[0059] ;

[0060] Among them, the This represents the measured spectral radiant flux of a fiber-optic broadband light source using a spectral radiance measurement device. Specifically, the measured spectral radiant flux here... Corrected spectral radiant flux The unit is W / nm, which stands for watts per nanometer. The measured diameter of standard optical fibers is also traceable to a metrological standard, which can be understood as a national standard.

[0061] S103: Calculate the radiative flux of the predetermined band based on the corrected spectral radiative flux.

[0062] Specifically, the range of the predetermined band is set based on actual needs. The total radiant flux of the band is obtained by integrating the corrected spectral radiant flux over the predetermined band. ;

[0063] In a preferred embodiment provided in this application, the predetermined band is [ l 1, l 2], the predetermined band [ l 1, l The radiation flux of [2] is as follows:

[0064] .

[0065] It is understood that the predetermined band [ l 1, l The radiation flux of [2] is the total radiation flux. It should be noted that the total radiative flux mentioned here... The unit is W, which is watt.

[0066] S104: Calculate the irradiance value of the fiber optic output port based on the radiant flux of the predetermined band, and use it as the standard value.

[0067] Specifically, given the known end-face area A of a standard optical fiber... When d is the diameter of a standard optical fiber, the irradiance value at the fiber output port is calculated as follows:

[0068] ;

[0069] Specifically, the irradiance value E mentioned here is used as a standard value, and its unit can be W / cm², that is, watts per square centimeter. In a preferred embodiment provided in this application, which mainly targets high irradiance scenarios, E typically refers to 0.5 W / cm² or higher.

[0070] S105: Measure the reading of the radiometer under test at the same fiber optic output port, compare the reading with the standard value, and obtain the calibration result.

[0071] After completing steps S101 to S104 above, detach the standard optical fiber from the integrating sphere and connect it directly to the optical fiber input port of the fiber-optic broadband radiometer under test. Obtain the reading E of the radiometer under test. t ;

[0072] It should be noted that the light received by the radiometer under test and the light in S104 come from the same light source and the same optical fiber. Therefore, the reading E of the radiometer under test is... t It should be equal to the standard value E calculated in S104. In a preferred embodiment provided in this application, the reading E of the radiometer under test... t It is the average of at least three measurements.

[0073] After completing the above measurements, the readings are compared with the standard values ​​to obtain the calibration results.

[0074] Specifically, the calibration results include: relative indication error and correction factor;

[0075] Relative indication error = ;

[0076] Correction factor = ;

[0077] Specifically, if the relative indication error is within the allowable range, the radiometer under test is considered qualified; if it exceeds the tolerance, a correction factor can be used to correct subsequent measurements. It can be understood that the allowable range for relative indication error can be determined based on the actual situation or relevant rules.

[0078] The above steps S101 to S105 constitute a complete calibration procedure. To ensure the accuracy and traceability of the calibration results, this application establishes the following... Figure 3 The traceability link for the measured values ​​is shown below:

[0079] like Figure 3As shown, the metrological traceability system of this application is divided into three levels: the National Institute of Metrology of China (including fine spectral measurement standard devices, spectral total radiant flux lamp calibration devices, spectral total radiant flux standard lamps, gauge blocks, etc.), the current level (including spectral line lamps, spectral radiant flux standard lamps, spectral radiant flux measurement systems, vernier calipers, etc.), and the lower level (the fiber optic broadband radiometer under test). It can be understood that the current level traces back to the National Institute of Metrology of China, and the lower level traces back to the current level.

[0080] In this application, the spectral radiant flux of the spectral radiant flux standard lamp is traced back to the spectral total radiant flux lamp calibration device and spectral total radiant flux standard lamp of the National Institute of Metrology, China. The diameter of the standard optical fiber 2 is traced back to the gauge blocks and vernier calipers of the National Institute of Metrology, China. That is, the spectral radiant flux of the spectral radiant flux standard lamp and the diameter of the standard optical fiber used to measure the fiber-optic broadband light source are both traced back to the measurement standard, i.e., the national standard.

[0081] The spectral radiometer is calibrated using a standard lamp, and the measurement reference is transferred to the spectral radiometer. Then, the standard irradiance value is calculated using the end-face area of ​​a standard optical fiber. Finally, this value is compared with the reading of the radiometer under test to complete the calibration, thus transferring the measurement data to the fiber-optic broadband radiometer under test, forming a complete measurement value transfer link. This measurement value traceability solves the problems of incomplete measurement value transfer and large differences in results between laboratories in existing technologies.

[0082] like Figure 2 As shown, the high-irradiance wideband radiometer calibration device provided in this application mainly includes: fiber optic wideband light source 1, standard optical fiber 2, standard optical fiber adapter 3, integrating sphere 4, baffle 5, spectral radiation flux standard lamp 6, spectral radiation flux standard lamp power supply system 7, and spectral radiation measurement device 8.

[0083] The fiber-optic broadband light source 1 is the light source to be calibrated, which can be a xenon lamp, LED lamp, or high-pressure mercury lamp, etc. Its output end is connected to a standard optical fiber 2, through which light is transmitted.

[0084] The diameter of standard fiber 2 is precisely measured, and its value is traceable to a metrological standard. The diameter of standard fiber 2 is used to calculate the fiber end-face area A, a key parameter for subsequently converting the radiant flux into a standard irradiance value. In this embodiment, three standard fibers with different diameters—3mm, 5mm, and 8mm—are prepared to accommodate the fiber optic interfaces of most commercially available fiber optic radiometers.

[0085] The standard fiber optic adapter 3 is installed on the light source input port of the integrating sphere 4. Different sizes of adapters can be replaced according to the fiber diameter to ensure that all the light emitted by the light source enters the integrating sphere.

[0086] The integrating sphere 4 is a hollow sphere with its inner wall coated with a highly reflective material (such as Spectralon) to provide a uniform diffuse light field. The integrating sphere has three ports: one is a light source input port for connecting to the standard fiber optic adapter 3; one is an output port for connecting to the spectral radiometry device 8; and the other is a calibration light source port for mounting the spectral radiometry standard lamp 6.

[0087] Baffles 5 are installed inside the integrating sphere, located at the light source input port, output port, and calibration light source port. The baffle at the light source input port is mainly used to prevent direct light from the fiber optic broadband light source from hitting the output port directly; the baffle at the calibration light source port is mainly used to prevent direct light from the spectral radiant flux standard lamp from hitting the output port directly; and the baffle at the output port is mainly used to prevent stray light from entering the integrating sphere and to avoid backscattering of light at the output port.

[0088] The combination of these three baffles ensures that all light reaching the output port comes from multiple diffuse reflections from the inner wall of the integrating sphere, thereby guaranteeing a uniform and stable light field distribution at the output port and providing accurate and reliable measurement conditions for the spectral radiation measurement device.

[0089] The spectral radiant flux standard lamp 6 is a standard light source with a known spectral radiant flux. It is installed at the calibration light source port of the integrating sphere and is used to calibrate the spectral radiant measurement device. Its value is traceable to a reference value. It is powered by the spectral radiant flux standard lamp power supply system 7. This device uses it to calibrate the spectral radiant measurement device 8.

[0090] The spectral radiation measuring device 8 is connected to the output port of the integrating sphere and is used to measure the spectral radiant flux of light coming out of the output port of the integrating sphere, in W / nm, i.e., watts per nanometer.

[0091] This method and apparatus were used to calibrate a fiber optic ultraviolet radiometer of a certain model, using a 365nm LED as the light source and a 5mm diameter fiber. After calibration, the calculated standard irradiance value was 2.35 W / cm², and the average of three readings from the radiometer was 2.28 W / cm², with a relative indication error of -3.0%. After five repeated measurements, the standard deviation was less than 1%, indicating that this method has good repeatability and accuracy.

[0092] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0093] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A calibration method using a high-irradiance broadband radiometer calibration device, the calibration device comprising: An integrating sphere, which is provided with a light source input port, an output port and a calibration light source port, is used to provide a uniform diffuse reflection light field; A spectral radiation measuring device is connected to the output port of the integrating sphere for measuring spectral radiant flux; A spectral radiation flux standard lamp is installed at the calibration light source port of the integrating sphere to calibrate the spectral radiation measurement device; At least one standard optical fiber is used to connect the fiber-optic broadband light source to the light source input port of the integrating sphere, so as to introduce the light source under test into the integrating sphere. The calibration method is characterized by comprising the following steps: Calibrate the spectral radiometry device and obtain the spectral correction coefficient; The spectral radiant flux of the fiber-optic broadband light source is measured and corrected using the spectral correction coefficient to obtain the corrected spectral radiant flux. Calculate the radiative flux of the predetermined band based on the corrected spectral radiative flux. Calculate the irradiance value at the fiber optic output port based on the radiant flux of the predetermined band, and use it as the standard value. The reading of the radiometer under test at the same fiber optic output port is measured, and the reading is compared with the standard value to obtain the calibration result; The calibration result is a relative indication error or a correction factor.

2. The method according to claim 1, characterized in that, The spectral correction coefficient is specifically: ； Among them, the The standard spectral radiant flux is the standard spectral radiant flux of a standard lamp. The values ​​are measured by the spectral radiometry device for the standard lamp.

3. The method according to claim 2, characterized in that, The corrected spectral radiant flux is specifically as follows: ； Among them, the This represents the measured spectral radiant flux of a fiber-optic broadband light source using a spectral radiation measurement device.

4. The method according to claim 3, characterized in that, The predetermined band is [ λ 1, λ 2], the predetermined band [ λ 1, λ The radiation flux of [2] is as follows: 。 5. The method according to claim 4, characterized in that, The specific irradiance value is as follows: ； Where A is the area of ​​the fiber end face.

6. The method according to claim 2, characterized in that, The spectral radiant flux of the standard lamp and the diameter of the standard optical fiber used to measure the fiber-optic broadband light source are both traceable to the measurement standard.

7. The method according to claim 1, characterized in that, The reading of the radiometer under test is the average of at least three measurements.

8. The method according to claim 1, characterized in that, The term "high irradiance" refers to the irradiance at the output end face of the optical fiber being greater than or equal to 0.5 W / cm².

9. The method according to claim 1, characterized in that, The integrating sphere has several baffles inside, which are respectively located at the light source input port, output port, and calibration light source port.

Images